Bio-based oil displacement gel fracturing fluid system and preparation method thereof

Abstract

The invention discloses a bio-based oil displacement gel fracturing fluid system and a preparation method thereof. The bio-based oil displacement gel fracturing fluid system comprises the following components: a guanidine gum thickening agent, an anti-swelling agent, a cleanup additive, a pH regulator, a cross-linking agent, a bio-based oil displacement agent, a synergist, a gel breaker and water. The bio-based oil displacement gel fracturing fluid system disclosed by the invention makes a remarkable breakthrough in the aspects of temperature resistance and salt resistance, and the system can keep excellent oil displacement performance under the conditions of high temperature up to 180 DEG C and mineralization degree up to 20 * 104 mg / L; meanwhile, the fracturing fluid also has the advantages of no toxicity, no pollution, degradability and the like, can obviously reduce secondary damage of a fracturing fluid system to a reservoir, and has important significance in improving the recovery ratio of a low-permeability tight oil reservoir and enhancing the development effect of the low-permeability tight oil reservoir.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of reservoir reconstruction oil production, and particularly relates to a bio-based oil displacement gel fracturing fluid system and a preparation method thereof. BACKGROUND

[0002] As a key component of global energy, oil production technology has been continuously developed with the increasing scarcity of resources. Traditional primary and secondary oil recovery technologies, such as relying on natural reservoir energy production, water or gas injection to supplement energy, etc., have played an important role in early production, but in the face of the growing demand for efficient oil production, they have gradually exposed technical bottlenecks. Although primary and secondary oil recovery technologies have made significant contributions in early production, in many reservoirs, the remaining oil saturation is still high, and a large amount of oil resources has not been effectively exploited. With the increasing difficulty of production, the cost also rises, making it difficult to maximize economic benefits.

[0003] Under this background, microbial oil production technology emerged as the times require. As one of the important methods of tertiary oil recovery, microbial oil production technology has received widespread attention due to its unique advantages. Microbial oil production mainly relies on the growth and metabolic activity of microorganisms to produce biological surfactants, biological polymers, gases, organic acids and other substances. These substances can change the wettability of rock surface, reduce oil-water interfacial tension, increase oil viscosity, change the percolation characteristics of oil layer, etc., so as to achieve the purpose of improving recovery efficiency.

[0004] However, the current research and development of microbial oil production technology is still in its infancy, and it faces many technical difficulties and limitations. On the one hand, the adaptability of microorganisms and related biological agents used in microbial oil production is narrow. Under different conditions of reservoir temperature, pressure, pH, etc., their activity and oil displacement effect are often difficult to guarantee, resulting in insufficient stability of the technology. For example, some microorganisms cannot grow and reproduce normally in high-temperature, high-salt or high-pressure reservoir environments, and cannot continuously produce effective oil displacement substances. On the other hand, the process flow of microbial oil production is relatively complex, and it is difficult to effectively compatible with traditional oil production processes, increasing the operation cost and difficulty. In addition, there are also problems such as control and optimization of microbial growth and metabolic products in the process of microbial oil production. How to precisely regulate the metabolic pathways of microorganisms to produce more beneficial substances for oil displacement while reducing the generation of harmful by-products is still a difficult problem to be solved.

[0005] Meanwhile, the fracturing fluid also plays a key role in oil exploitation, and its performance directly affects the fracturing effect and recovery rate. The traditional fracturing fluid has problems such as great damage to oil reservoir and poor environmental friendliness. In the fracturing process, the filtrate of the fracturing fluid is easy to invade the oil layer, change the physical and chemical properties of the oil layer, cause the oil layer to be blocked, and reduce the recovery rate. Moreover, part of the fracturing fluid contains toxic and harmful chemical substances, which are difficult to recover completely after use and pollute the environment. In view of this, in order to overcome the shortcomings of the prior art, it is urgent to develop a stable and efficient bio-based oil displacement gel fracturing fluid system to meet the development needs of modern oil exploitation technology and reduce the negative impact on the environment. SUMMARY

[0006] The present application provides a bio-based oil displacement gel fracturing fluid system and a preparation method thereof to solve the above technical problems. The fracturing fluid system of the present application ingeniously combines the advantages of microbial oil recovery technology and fracturing fluid technology, can stably improve the oil recovery rate, is environmentally friendly, and is well adapted to the reservoir conditions and existing oil recovery process, meeting the increasing demand for efficient and green oil recovery in the oil industry.

[0007] In a first aspect, the present application provides a bio-based oil displacement gel fracturing fluid system, which is realized by the following technical scheme.

[0008] The bio-based oil displacement gel fracturing fluid system comprises the following components in parts by weight: 0.25-0.45 parts of guar gum thickening agent, 0.15-0.35 parts of anti-swelling agent, 0.15-0.35 parts of cleanup agent, 0.05-0.15 parts of pH regulator, 0.15-0.35 parts of crosslinking agent, 0.5-3 parts of bio-based oil displacement agent, 0.5-1.5 parts of synergist, 0.05-0.15 parts of gel breaker, and 100 parts of water.

[0009] Further, the preparation method of the bio-based oil displacement agent is as follows:

[0010] The Bacillus subtilis BZ-1 strain is activated in LB medium, a single colony is picked and inoculated in LB liquid medium, and cultured at 35-40℃ and 180-200rpm for 12-24h. Then, the culture is transferred to LB liquid medium at an inoculation amount of 1%, and cultured at 35-40℃ and 180-200rpm until the OD600 is 0.5-0.8. Then, the culture is transferred to a flask containing fermentation medium at an inoculation amount of 5%, and cultured at 35-40℃ and 180-200rpm for 24-48h. Then, the expanded culture is added to a fermentation tank containing fermentation medium at an inoculation amount of 5%, and fermented at 35-40℃ for 48-72h. Then, the fermentation broth is preliminarily filtered, and the obtained filtrate is broken and finely filtered. Subsequently, the bio-based oil displacement agent is obtained by compounding the filtrate with decyl alkyl hydroxypropyl sulfobetaine and fatty alcohol polyoxyethylene ether ammonium sulfate at a mass ratio of 10:2:1.

[0011] The bacillus subtilis BZ-1 was preserved in the China General Microbiological Culture Collection Center on November 15, 2024, and the preservation number is CGMCC No. 32653.

[0012] Further, the fermentation medium comprises the following components in parts by weight: 5 parts of glucose, 5 parts of sodium acetate, 1 part of ammonium sulfate, 4.8 parts of dipotassium hydrogen phosphate, 1.5 parts of potassium dihydrogen phosphate, 0.5 parts of trisodium citrate, 0.5 parts of magnesium sulfate, 0.2 parts of yeast extract, 0.01 parts of calcium carbonate, 0.002 parts of manganese sulfate, 0.1 parts of ferrous sulfate, 0.0004 parts of nickel chloride, 0.0004 parts of zinc sulfate, 0.0002 parts of ferric chloride, 0.0002 parts of sodium molybdate, and distilled water to 1000 parts.

[0013] Further, the guar gum thickening agent is one or more of guar gum, hydroxypropyl guar gum, and carboxymethyl guar gum.

[0014] Further, the anti-swelling agent is selected from one or more of potassium chloride, ammonium chloride, and potassium sulfate.

[0015] Further, the cleanup agent is selected from one or more of dodecyl dimethyl betaine, fatty alcohol polyoxyethylene ether (AEO-7), and sodium dodecyl benzene sulfonate.

[0016] Further, the crosslinking agent is selected from one or more of tetrabutyl titanate, zirconium oxychloride octahydrate, and boric acid triethanolamine complex.

[0017] Further, the synergist comprises the following components in parts by weight: 5-10 parts of lipopeptide, 5-10 parts of rhamnolipid, and distilled water to 1000 parts.

[0018] Further, the pH regulator is selected from one or more of sodium carbonate, sodium hydroxide, and potassium hydroxide; and the breaker is one or more of ammonium persulfate and potassium persulfate.

[0019] In a second aspect, the present application provides a preparation method of a bio-based oil displacement gel fracturing fluid system, which is realized through the following technical scheme.

[0020] A preparation method of the above-mentioned bio-based oil displacement gel fracturing fluid system, comprising the following steps:

[0021] S1. A predetermined amount of guar gum thickening agent, anti-swelling agent, cleanup agent, and pH regulator are added to water in sequence while stirring, and the mixture is uniformly mixed and then left to swell to obtain a raw gel solution;

[0022] S2. A prescribed amount of lipopeptide is added to an alkaline aqueous solution with a pH of 9.0-10.0 to form a dispersion under stirring, then rhamnolipid is added, and the mixture is stirred mechanically at room temperature for 1-2 h to obtain the synergist;

[0023] S3. The crosslinking agent, the bio-based oil displacement agent, the synergist and the gel breaker are sequentially added to the original gel solution, and the mixture is stirred uniformly to obtain the bio-based oil displacement gel fracturing fluid system.

[0024] The present application has the following beneficial effects.

[0025] (1) The bio-based oil displacement gel fracturing fluid system of the present application has made a significant breakthrough in the temperature resistance and salt tolerance, and the system can maintain excellent oil displacement performance under the conditions of a high temperature of up to 180℃ and a salinity of up to 20×10 4 mg / L;

[0026] (2) The bio-based oil displacement gel fracturing fluid system of the present application not only fully utilizes the excellent performance advantages of the bio-based oil displacement agent, but also has many advantages such as non-toxicity, non-pollution and biodegradability, and can significantly reduce the secondary damage of the fracturing fluid system to the reservoir, which is of great significance to improve the recovery rate of low-permeability tight oil reservoirs and enhance the development effect. BRIEF DESCRIPTION OF DRAWINGS

[0027] Figure 1 is the phylogenetic evolution tree of Bacillus subtilis BZ-1 of the present application (wherein, A: phylogenetic tree diagram; B: phylogenetic tree diagram of srfA gene);

[0028] Figure 2 is the rheological curve diagram of the fracturing fluid containing the bio-based oil displacement agent prepared in Example 6 of the present application;

[0029] Figure 3 is the rheological curve diagram of the fracturing fluid not containing the bio-based oil displacement agent prepared in Comparative Example 1 of the present application;

[0030] Figure 4 is the well construction curve diagram of the present application;

[0031] Figure 5 is the comparison diagram of the maximum daily oil production of the test well and the adjacent well of the present application. DETAILED DESCRIPTION

[0032] The application will be further described below in combination with the drawings and examples.

[0033] The Bacillus subtilis BZ-1 strain is separated from an oil-contaminated soil sample in Dagang Oilfield in Tianjin, and the separation and culture method of the strain is as follows: the soil sample is weighed and suspended in distilled water, glass beads are added for stirring, ultrasonic treatment is performed, and the sample is left overnight; the next day, the supernatant is vacuum filtered, and the filtrate is sterilized to prepare a soil leaching solution, which is stored at room temperature for standby use. 5 g of the soil sample stored in a 4℃ refrigerator is dissolved in 100 mL of sterile normal saline, glass beads are added for stirring, and the sample is shaken at 37℃ for 30 min; gradient dilution (dilution gradient is 10 -1 , 10 -2 , 10 -3 , 10 -4 , 10 -5 ) is performed with sterile water, 50 μL of the bacterial suspension in each dilution gradient is coated on an LB solid culture medium containing 20% soil leaching solution, and the sample is cultured for 2-3 days; different single colonies are picked and plated for streaking until single colonies are separated. Different single colonies are inoculated in 5 mL of fermentation medium, and the sample is cultured at 37℃ and 200 rpm for 2-3 days; 2 μL of the fermentation liquid is used for oil ring measurement, and 2 μL of the fermentation liquid is inoculated in oil-containing inorganic salt solid culture medium (the inorganic salt solid culture medium is prepared with the following components: dipotassium hydrogen phosphate 2.0 g, potassium dihydrogen phosphate 1.0 g, ammonium nitrate 2.0 g, magnesium sulfate heptahydrate 0.2 g, sodium chloride 5.0 g, calcium chloride 0.02 g, agar 15 g, pH is adjusted to 7.2, and the volume is adjusted to 1000 mL with distilled water; after the plate is solidified, 1.5% (v / v) of crude oil is uniformly coated on the surface to form a uniform oil layer). The inoculated culture medium is placed at 37℃ for static culture for 2 days, the size of the ring-shaped area formed on the culture medium is observed, fresh bacterial liquid with large oil ring is mixed with 20% glycerol in a glycerol tube, and the sample is stored in a -80℃ refrigerator.

[0034] Genomic DNA of the strain was extracted and purified, and PCR amplification was performed using 27F: 5'-AGAGTTTGATCMTGGCTCAG-3' (SEQ ID NO. 1) and 1541R: 5'-AAGGAGGTGATCCAGCC-3' (SEQ ID NO. 2) primers as templates. The PCR product was detected by 1% agarose gel electrophoresis, and the gel was purified and sequenced. The sequencing results were analyzed by BLAST software, and the homology was compared with the 16S rRNA gene in GenBank. The genetic distance was calculated by MEGA 5.0 software, and the phylogenetic tree was constructed by the Neighbor-Joining distance matrix method. The genomic DNA was used as a template, and the srfA F: 5'-ATGTCAGAACAACAGCAACAGC-3' (SEQ ID NO. 3) and srfA R: 5'-TTATAAAAGCTTCGTCCATTGC-3' (SEQ ID NO. 4) primers were used to amplify the lipopeptide gene srfA, and the phylogenetic tree of the srfA gene was established by the above method. Figure 1 is the phylogenetic tree of Bacillus subtilis, and Figure 1 It can be seen that the 16S rRNA of the strain BZ-1 has a similarity of 99% with Bacillus subtilis. The strain contains the lipopeptide gene srfA, indicating that the strain BZ-1 is a Bacillus subtilis containing srfA.

[0035] The following examples are the preparation of a biological-based oil displacement gel fracturing fluid system using Bacillus subtilis BZ-1 screened by the application.

[0036] Rhamnolipid (CAS: 869062-42-0) and lipopeptide (CAS: 171263-26-6) used in the following examples of the application were purchased from Macklin.

[0037] Hydroxypropyl guar gum used in the following examples of the application was purchased from Guangrao Liuhui Chemical Co., Ltd.

[0038] Decyl hydroxypropyl sulfobetaine used in the following examples of the application was purchased from Jinan Yunuo Chemical Co., Ltd.

[0039] Fatty alcohol polyoxyethylene ether ammonium sulfate used in the following examples of the application was purchased from Shandong Youxiao Chemical Technology Co., Ltd.

[0040] Triethanolamine borate complex used in the following examples of the application was purchased from Sichuan Aijie Technology Co., Ltd.

[0041] Example 1

[0042] A preparation method of a biological-based oil displacement gel fracturing fluid system, comprising the following steps:

[0043] S1: 1.4 g of hydroxypropyl guar gum, 0.6 g of potassium chloride, 1 g of dodecyl dimethyl betaine, and 0.6 g of sodium carbonate were sequentially added to 400 mL of water under stirring, and after mixing and swelling, a base glue solution was obtained;

[0044] S2: Bacillus subtilis BZ-1 strain was activated with LB medium, a single colony was inoculated in LB liquid medium, and cultured at 37°C, 200 rpm for 12 h, then inoculated in 500 mL of LB liquid medium at 1%, and cultured at 37°C, 200 rpm until OD600 was 0.5, then inoculated in a triangular flask containing 2 L of fermentation medium at 5%, and cultured at 37°C, 200 rpm for 48 h, then the culture liquid in the triangular flask was inoculated in a 10 L fermentation tank containing fermentation medium at 5%, and fermented at 37°C for 60 h, then the fermentation liquid was preliminarily filtered, the obtained filtrate was broken and then finely filtered, then compounded with decyl hydroxypropyl sulfobetaine, fatty alcohol polyoxyethylene ether ammonium sulfate at a mass ratio of 10:2:1, and finally a bio-based oil displacement agent was obtained;

[0045] The fermentation medium formula is 5 g of glucose, 5 g of sodium acetate, 1 g of ammonium sulfate, 4.8 g of dipotassium hydrogen phosphate, 1.5 g of potassium dihydrogen phosphate, 0.5 g of trisodium citrate, 0.5 g of magnesium sulfate, 0.2 g of yeast extract, 0.1 g of ferrous sulfate, 0.01 g of calcium carbonate, 0.002 g of manganese sulfate, 0.0004 g of nickel chloride, 0.0004 g of zinc sulfate, 0.0002 g of ferric chloride, 0.0002 g of sodium molybdate, and distilled water to 1000 mL (1 liter);

[0046] S3: 100 mL of water was measured, and the pH was adjusted to 9.5 with sodium hydroxide to obtain an alkaline aqueous solution, 0.5 g of lipopeptide was slowly added under high-speed shearing stirring, and shearing was continued for 5 minutes; then 1.0 g of rhamnolipid was slowly added under mechanical stirring, and stirring was continued for 1 hour until the system was uniform, and a synergist was obtained;

[0047] S4: 1 g of boric acid triethanolamine complex, 2 g of bio-based oil displacement agent, 2 g of synergist, and 0.2 g of ammonium persulfate were sequentially added to the base glue solution, and stirred uniformly to obtain a bio-based oil displacement gel fracturing fluid system.

[0048] Example 2

[0049] A preparation method of a bio-based oil displacement gel fracturing fluid system, comprising the following steps:

[0050] S1: 1.4 g of hydroxypropyl guar gum, 0.6 g of potassium chloride, 1 g of dodecyl dimethyl betaine, 0.6 g of sodium carbonate were added into 400 mL of water in sequence under stirring, and after mixing and swelling, a raw glue solution was obtained;

[0051] S2: The Bacillus subtilis BZ-1 strain was activated with LB medium, a single colony was inoculated into LB liquid medium, and cultured at 37°C, 200 rpm for 12 h. Then, the culture was transferred into 500 mL of LB liquid medium at an inoculation amount of 1%, and cultured at 37°C, 200 rpm until the OD600 was 0.5. Then, the culture was transferred into a 2 L flask containing fermentation medium at an inoculation amount of 5%, and cultured at 37°C, 200 rpm for 48 h. Then, the culture in the flask was inoculated into a 10 L fermenter containing fermentation medium at an inoculation amount of 5%, and fermented at 37°C for 60 h. The fermentation broth was preliminarily filtered, and the obtained filtrate was broken and then finely filtered. Then, the filtrate was compounded with decyl hydroxypropyl sulfobetaine, fatty alcohol polyoxyethylene ether ammonium sulfate at a mass ratio of 10:2:1 to obtain a bio-based oil displacement agent.

[0052] The fermentation medium formula is 5 g of glucose, 5 g of sodium acetate, 1 g of ammonium sulfate, 4.8 g of dipotassium hydrogen phosphate, 1.5 g of potassium dihydrogen phosphate, 0.5 g of trisodium citrate, 0.5 g of magnesium sulfate, 0.2 g of yeast extract, 0.1 g of ferrous sulfate, 0.01 g of calcium carbonate, 0.002 g of manganese sulfate, 0.0004 g of nickel chloride, 0.0004 g of zinc sulfate, 0.0002 g of ferric chloride, 0.0002 g of sodium molybdate, and distilled water to 1000 mL (1 liter);

[0053] S3: 100 mL of water was measured, and the pH was adjusted to 9.5 with sodium hydroxide to obtain an alkaline aqueous solution. Then, 0.5 g of lipopeptide was slowly added under high-speed shearing stirring, and the shearing was continued for 5 minutes. Then, 1.0 g of rhamnolipid was slowly added under mechanical stirring, and the stirring was continued for 1 hour until the system was uniform, thereby obtaining a synergist;

[0054] S4: 1 g of boric acid triethanolamine complex, 4 g of bio-based oil displacement agent, 2 g of synergist, and 0.2 g of ammonium persulfate were added into the raw glue solution in sequence, and stirred uniformly to obtain a bio-based oil displacement gel fracturing fluid system.

[0055] Example 3

[0056] A preparation method of a bio-based oil displacement gel fracturing fluid system, comprising the following steps:

[0057] S1: 1.4 g of hydroxypropyl guar gum, 0.6 g of potassium chloride, 1 g of dodecyl dimethyl betaine, 0.6 g of sodium carbonate were added into 400 mL of water in sequence under stirring, and after mixing and swelling, a raw glue solution was obtained;

[0058] S2: Activate Bacillus subtilis BZ-1 strain with LB medium, pick single colony and inoculate in LB liquid medium, cultivate at 37℃, 200rpm for 12h, transfer to 500mL LB liquid medium at 1% inoculation amount, cultivate at 37℃, 200rpm until OD600 is 0.5, then transfer to a flask containing 2L fermentation medium at 5% inoculation amount, cultivate at 37℃, 200rpm for 48h, transfer the flask-cultured bacteria liquid to a 10L fermenter containing fermentation medium at 5% inoculation amount, ferment at 37℃ for 60h, perform preliminary filtration on the fermentation liquid, perform fine filtration on the obtained filtrate after cell wall disruption, then compound with decyl alkyl hydroxypropyl sulfobetaine, fatty alcohol polyoxyethylene ether ammonium sulfate at a mass ratio of 10:2:1, and finally obtain a bio-based oil displacement agent;

[0059] The fermentation medium formula is 5g of glucose, 5g of sodium acetate, 1g of ammonium sulfate, 4.8g of potassium hydrogen phosphate, 1.5g of potassium dihydrogen phosphate, 0.5g of trisodium citrate, 0.5g of magnesium sulfate, 0.2g of yeast extract, 0.1g of ferrous sulfate, 0.01g of calcium carbonate, 0.002g of manganese sulfate, 0.0004g of nickel chloride, 0.0004g of zinc sulfate, 0.0002g of ferric chloride, 0.0002g of sodium molybdate, and distilled water to 1000mL (i.e. 1 liter);

[0060] S3: Measure 100mL of water, adjust the pH to 9.5 with sodium hydroxide to obtain an alkaline aqueous solution, slowly add 0.5g of lipopeptide under high-speed shearing stirring, continue shearing for 5 minutes; then slowly add 1.0g of rhamnolipid under mechanical stirring, continue stirring for 1 hour until the system is uniform, and the synergist is obtained;

[0061] S4: Add 1g of boric acid triethanolamine complex, 6g of bio-based oil displacement agent, 2g of synergist and 0.2g of ammonium persulfate to the original glue solution in sequence, stir uniformly to obtain a bio-based oil displacement gel fracturing fluid system.

[0062] Example 4

[0063] A preparation method of a bio-based oil displacement gel fracturing fluid system, comprising the following steps:

[0064] S1: Add 1.4g of hydroxypropyl guar gum, 0.6g of potassium chloride, 1g of dodecyl dimethyl betaine, and 0.6g of sodium carbonate to 400mL of water in sequence while stirring, mix uniformly, and then stand for swelling to obtain an original glue solution;

[0065] S2: Activate the Bacillus subtilis BZ-1 strain with LB medium, pick a single colony and inoculate it in LB liquid medium, cultivate at 37°C, 200 rpm for 12h, then transfer it to 500mL LB liquid medium at 1% inoculation amount, cultivate at 37°C, 200 rpm until OD600 is 0.5, then transfer it to a triangular flask containing 2L fermentation medium at 5% inoculation amount, cultivate at 37°C, 200 rpm for 48h, then transfer the culture liquid in the triangular flask to a 10L fermenter containing fermentation medium at 5% inoculation amount, ferment at 37°C for 60h, then perform preliminary filtration on the fermentation liquid, perform fine filtration on the obtained filtrate after cell wall disruption, then compound it with decyl hydroxypropyl sulfobetaine, fatty alcohol polyoxyethylene ether ammonium sulfate at a mass ratio of 10:2:1, and finally obtain a bio-based oil displacement agent;

[0066] The fermentation medium formula is 5g of glucose, 5g of sodium acetate, 1g of ammonium sulfate, 4.8g of potassium hydrogen phosphate, 1.5g of potassium dihydrogen phosphate, 0.5g of trisodium citrate, 0.5g of magnesium sulfate, 0.2g of yeast extract, 0.1g of ferrous sulfate, 0.01g of calcium carbonate, 0.002g of manganese sulfate, 0.0004g of nickel chloride, 0.0004g of zinc sulfate, 0.0002g of ferric chloride, 0.0002g of sodium molybdate, and distilled water to 1000mL (i.e. 1 liter);

[0067] S3: Measure 100mL of water, adjust the pH to 9.5 with sodium hydroxide to obtain an alkaline aqueous solution, slowly add 0.5g of lipopeptide under high-speed shearing stirring, continue shearing for 5 minutes; then slowly add 1.0g of rhamnolipid under mechanical stirring, continue stirring for 1 hour until the system is uniform, and obtain a synergist;

[0068] S4: Add 1g of boric acid triethanolamine complex, 8g of bio-based oil displacement agent, 2g of synergist and 0.2g of ammonium persulfate to the original glue solution in sequence, stir uniformly to obtain a bio-based oil displacement gel fracturing fluid system.

[0069] Example 5

[0070] S1: Add 1.4g of hydroxypropyl guar gum, 0.6g of potassium chloride, 1g of dodecyl dimethyl betaine, and 0.6g of sodium carbonate to 400mL of water in sequence while stirring, mix uniformly, and then stand for swelling to obtain an original glue solution;

[0071] S2: Activate the Bacillus subtilis BZ-1 strain with LB medium, pick a single colony and inoculate it in LB liquid medium, cultivate at 37℃, 200rpm for 12h, then transfer it to 500mL LB liquid medium at 1% inoculation amount, cultivate at 37℃, 200rpm until OD600 is 0.5, then transfer it to a flask containing 2L fermentation medium at 5% inoculation amount, cultivate at 37℃, 200rpm for 48h, then transfer the flask-cultivated bacterial liquid to a 10L fermenter containing fermentation medium at 5% inoculation amount, ferment at 37℃ for 60h, then perform preliminary filtration on the fermentation liquid, perform fine filtration on the obtained filtrate after cell wall disruption, then compound it with decyl hydroxypropyl sulfonated betaine, fatty alcohol polyoxyethylene ether ammonium sulfate at a mass ratio of 10:2:1, and finally obtain a bio-based oil displacement agent;

[0072] The fermentation medium formula is 5g of glucose, 5g of sodium acetate, 1g of ammonium sulfate, 4.8g of potassium hydrogen phosphate, 1.5g of potassium dihydrogen phosphate, 0.5g of trisodium citrate, 0.5g of magnesium sulfate, 0.2g of yeast extract, 0.1g of ferrous sulfate, 0.01g of calcium carbonate, 0.002g of manganese sulfate, 0.0004g of nickel chloride, 0.0004g of zinc sulfate, 0.0002g of ferric chloride, 0.0002g of sodium molybdate, and distilled water to 1000mL (i.e. 1 liter);

[0073] S3: Measure 100mL of water, adjust the pH to 9.5 with sodium hydroxide to obtain an alkaline aqueous solution, slowly add 0.5g of lipopeptide under high-speed shearing stirring, continue shearing for 5 minutes; then slowly add 1.0g of rhamnolipid under mechanical stirring, continue stirring for 1 hour until the system is uniform, and obtain a synergist;

[0074] S4: Add 1g of boric acid triethanolamine complex, 10g of bio-based oil displacement agent, 2g of synergist, and 0.2g of ammonium persulfate to the original glue solution in sequence, stir uniformly to obtain a bio-based oil displacement gel fracturing fluid system.

[0075] Example 6

[0076] S1: Add 1.4g of hydroxypropyl guar gum, 0.6g of potassium chloride, 1g of dodecyl dimethyl betaine, and 0.6g of sodium carbonate to 400mL of water in sequence while stirring, mix uniformly, and then stand for swelling to obtain an original glue solution;

[0077] S2: Activate Bacillus subtilis BZ-1 strain with LB medium, pick single colony and inoculate in LB liquid medium, cultivate at 37℃, 200rpm for 12h, transfer to 500mL LB liquid medium with 1% inoculation amount, cultivate at 37℃, 200rpm until OD600 is 0.5, then transfer to a flask containing 2L fermentation medium with 5% inoculation amount, cultivate at 37℃, 200rpm for 48h, transfer the flask-cultured bacteria liquid to a 10L fermenter containing fermentation medium with 5% inoculation amount, ferment at 37℃ for 60h, perform preliminary filtration on the fermentation liquid, perform fine filtration on the obtained filtrate after cell wall disruption, then compound with decyl alkyl hydroxypropyl sulfobetaine, fatty alcohol polyoxyethylene ether ammonium sulfate at a mass ratio of 10:2:1, and finally obtain a bio-based oil displacement agent;

[0078] The fermentation medium formula is 5g of glucose, 5g of sodium acetate, 1g of ammonium sulfate, 4.8g of dipotassium hydrogen phosphate, 1.5g of potassium dihydrogen phosphate, 0.5g of trisodium citrate, 0.5g of magnesium sulfate, 0.2g of yeast extract, 0.1g of ferrous sulfate, 0.01g of calcium carbonate, 0.002g of manganese sulfate, 0.0004g of nickel chloride, 0.0004g of zinc sulfate, 0.0002g of ferric chloride, 0.0002g of sodium molybdate, and distilled water to 1000mL (i.e., 1 liter);

[0079] S3: Measure 100mL of water, adjust the pH to 9.5 with sodium hydroxide to obtain an alkaline aqueous solution, slowly add 0.5g of lipopeptide under high-speed shearing stirring, continue shearing for 5 minutes; then slowly add 1.0g of rhamnolipid under mechanical stirring, continue stirring for 1 hour until the system is uniform, and the synergist is obtained;

[0080] S4: Add 1g of boric acid triethanolamine complex, 12g of bio-based oil displacement agent, 2g of synergist, and 0.2g of ammonium persulfate to the original glue solution, stir uniformly to obtain a bio-based oil displacement gel fracturing fluid system.

[0081] Comparative Example 1

[0082] A preparation method of a gel fracturing fluid system, comprising the following steps:

[0083] S1: Add 1.4g of hydroxypropyl guar gum, 0.6g of potassium chloride, 1g of dodecyl dimethyl betaine, and 0.6g of sodium carbonate to 400mL of water under stirring, mix uniformly, and then stand for swelling to obtain an original glue solution;

[0084] S2: Add 1g of boric acid triethanolamine complex and 0.2g of ammonium persulfate to the original glue solution, stir uniformly to obtain an original gel fracturing fluid system.

[0085] Comparative Example 2

[0086] A preparation method of a gel fracturing fluid system, comprising the following steps:

[0087] S1: 1.4 g of hydroxypropyl guar gum, 0.6 g of potassium chloride, 1 g of dodecyl dimethyl betaine, and 0.6 g of sodium carbonate are sequentially added to 400 mL of water with stirring, and after mixing, swelling is performed, to obtain a raw gel solution;

[0088] S2: 100 mL of water is measured, and sodium hydroxide is used to adjust the pH to 9.5 to obtain an alkaline aqueous solution; 0.5 g of lipopeptide is slowly added under high-speed shearing stirring, and shearing is continued for 5 minutes; then 1.0 g of rhamnolipid is slowly added under mechanical stirring, and stirring is continued for 1 hour until the system is uniform, to obtain a synergist;

[0089] S3: 1 g of boric acid triethanolamine complex, 2 g of the synergist, and 0.2 g of ammonium persulfate are sequentially added to the raw gel solution, and stirring is performed until uniform, to obtain an original gel fracturing fluid system.

[0090] Comparative Example 3

[0091] A preparation method of a bio-based oil displacement gel fracturing fluid system, comprising the following steps:

[0092] S1: 1.4 g of hydroxypropyl guar gum, 0.6 g of potassium chloride, 1 g of dodecyl dimethyl betaine, and 0.6 g of sodium carbonate are sequentially added to 400 mL of water with stirring, and after mixing, swelling is performed, to obtain a raw gel solution;

[0093] S2: Bacillus subtilis BZ-1 strain is activated with LB medium, a single colony is inoculated in LB liquid medium, and culture is performed at 37°C and 200 rpm for 12 h; inoculation is performed in 500 mL of LB liquid medium at a 1% inoculation amount, culture is performed at 37°C and 200 rpm until OD600 is 0.5, inoculation is performed in a flask containing 2 L of fermentation medium at a 5% inoculation amount, and culture is performed at 37°C and 200 rpm for 48 h; the bacteria liquid obtained by expansion culture in the flask is inoculated in a 10 L fermentation tank containing the fermentation medium at a 5% inoculation amount, and fermentation is performed at 37°C for 60 h; the fermentation liquid is subjected to preliminary filtration, the obtained filtrate is subjected to cell wall breaking treatment and fine filtration, and then is compounded with decyl hydroxypropyl sulfobetaine, fatty alcohol polyoxyethylene ether ammonium sulfate at a mass ratio of 10:2:1, to finally obtain a bio-based oil displacement agent;

[0094] The fermentation medium formula is glucose 5g, sodium acetate 5g, ammonium sulfate 1g, dipotassium hydrogen phosphate 4.8g, potassium dihydrogen phosphate 1.5g, trisodium citrate 0.5g, magnesium sulfate 0.5g, yeast extract 0.2g, ferrous sulfate 0.1g, calcium carbonate 0.01g, manganese sulfate 0.002g, nickel chloride 0.0004g, zinc sulfate 0.0004g, ferric chloride 0.0002g, sodium molybdate 0.0002g, and distilled water is constant volume to 1000ml (i.e. 1 liter);

[0095] S3: 1g boric acid triethanolamine complex, 2g bio-based oil displacement agent and 0.2g ammonium persulfate were added into the original glue solution in turn, and the mixture was stirred uniformly to obtain a bio-based oil displacement gel fracturing fluid system.

[0096] Performance detection

[0097] During the fracturing operation, the fracturing fluid needs to have excellent thermal stability and shear stability. Specifically, under given temperature and shear rate conditions, it must maintain a certain viscosity to ensure that the fracture can be successfully opened and extended, and the proppant can be efficiently carried. During the process of flowing through the pipeline, perforation hole and finally entering the formation, the fracturing fluid will face high mechanical shear, and at the same time, the temperature will also rise. The double factors superimpose each other, which aggravates the thermal degradation and chemical degradation possibility of the fracturing fluid, resulting in the decrease of the apparent viscosity of the fracturing fluid in the formation, thereby causing the poor sand carrying performance and the easy occurrence of filtration loss. Based on this, it is particularly crucial to evaluate the temperature resistance and shear resistance performance of the fracturing fluid.

[0098] In this experiment, first, the Hake RS6000 high temperature and high pressure rheometer was used to conduct temperature resistance and shear resistance experiments on the fracturing fluids in Example 6 and Comparative Example 1 at a temperature of 100°C and a shear rate of 170s -1 The experimental results are shown in Figure 2 , 3 From the rheological curves of the two gel fracturing fluids, it can be found that whether the bio-based oil displacement agent and the synergist are added or not, the temperature resistance and shear resistance performance of the gel does not change significantly. This experimental result further confirms that the addition of the bio-based oil displacement agent and the synergist does not have a negative impact on the performance of the gel fracturing fluid, indicating that the bio-based oil displacement agent has good compatibility with the gel fracturing fluid.

[0099] To further evaluate the performance of the bio-based oil displacement fracturing fluid, static oil washing capacity tests of different concentrations of bio-based oil displacement fracturing fluid (Examples 1-6, Comparative Examples 1-3) were subsequently carried out, and the experimental scheme was as follows: different concentrations of bio-based oil displacement fracturing fluid were placed in a water bath, and after constant temperature at 90°C for 2 hours, the bio-based oil displacement fracturing fluid was completely broken to form a bio-based oil displacement fracturing fluid broken liquid. Take 100 mL beaker containing oil sand, accurately take 50 mL of different concentrations of bio-based oil displacement fracturing fluid broken liquid, and place it in a 50°C environment for 24 hours, then shake to promote oil to escape from the oil sand, and accurately measure the amount of oil washed out by the bio-based oil displacement fracturing fluid broken liquid. The oil washing rate is calculated according to the formula: oil washing rate = (V2 / V1) x 100%, wherein V1 is the original oil content of the oil sand (mL), and V2 is the amount of oil washed out (mL). The experimental results are shown in Table 1.

[0100] Table 1 Static oil washing rate of different concentrations of bio-based oil displacement fracturing fluid broken liquid

[0101]

[0102] The results show that the oil washing rate of Comparative Example 1 (without bio-based oil displacement agent and synergist) is only 38.7%, which represents the benchmark performance of the base fracturing fluid system; the oil washing rate of Comparative Example 2 (containing only a synergist, without a bio-based oil displacement agent) is 40.2%, which is basically the same as Comparative Example 1, indicating that the use of a synergist (lipopeptide + rhamnolipid) alone does not significantly improve the oil washing efficiency; the oil washing rate of Comparative Example 3 (containing 0.5% bio-based oil displacement agent, without a synergist) is 75.8%, which is better than Comparative Examples 1 and 2, proving that the bio-based oil displacement agent itself has good oil displacement ability, but is still significantly lower than Example 1; the oil washing rate of Example 1 is significantly higher than that of Comparative Example 3, indicating that there is a significant synergistic effect between the bio-based oil displacement agent and the synergist (lipopeptide, rhamnolipid). In this invention, the bio-based oil displacement agent provides the basic interfacial activity and oil displacement ability, the lipopeptide further enhances the interfacial activity and emulsification efficiency, and the rhamnolipid can significantly improve the wettability of the rock surface. The synergistic effect of the three reduces the oil-water interfacial tension, changes the wettability of the rock, and forms an efficient oil displacement network.

[0103] In addition, the concentration of the bio-based oil displacement agent is positively correlated with the oil washing rate, and as the concentration increases, the oil washing rate also increases. When the concentration increases to 2%, the oil washing rate tends to be stable, reaching a saturation state, so the optimal concentration range for use in the fracturing fluid system is 0.5-2%. In addition, the oil displacement efficiency of this oil displacement fracturing fluid is significantly high, and even under low concentration conditions, the oil washing rate can still be maintained at more than 80%, with excellent performance.

[0104] The application evaluates the temperature resistance and salt tolerance of the bio-based oil displacement gel fracturing fluid system. The specific test method for temperature resistance evaluation is as follows: prepare multiple samples of bio-based oil displacement fracturing fluid (configured according to Example 4), and place them in a water bath, and after constant temperature at 90°C for 2 hours, completely gel breaking to form bio-based oil displacement fracturing fluid gel breaking liquid. Select several 100mL beakers, and add the same amount of oil-containing sand to each beaker to ensure the same original oil content (V1) of the oil sand. Place the beakers in different temperature constant temperature water bath environments, and accurately measure 50mL of bio-based oil displacement fracturing fluid gel breaking liquid into each beaker under the corresponding temperature condition, and place it in the corresponding temperature constant temperature water bath for 24 hours, then shake the beaker to promote the oil to escape from the oil sand, and accurately measure the amount of oil washed out (V2).

[0105] The specific test method for salt tolerance evaluation is as follows: prepare multiple samples of bio-based oil displacement fracturing fluid (configured according to Example 5), and configure a series of salt solutions with different salinities to simulate the salinity environment of formation water. Mix the bio-based oil displacement fracturing fluid (configured according to Example 5) with the salt solutions with different salinities at a ratio of 4:1 to prepare fracturing fluid systems with different salinities, and place them in a water bath at 90°C for 2 hours to completely gel break and form bio-based oil displacement fracturing fluid gel breaking liquid. Select several 100mL beakers, and add the same amount of oil-containing sand to each beaker to ensure the same original oil content of the oil sand, and add 50mL of fracturing fluid gel breaking liquid to the beakers containing oil-containing sand, respectively. After standing at 50°C for 24 hours, shake the beaker to promote oil to escape, and accurately measure the amount of oil washed out. Calculate the oil washing rate of the fracturing fluid under different temperature and salinity conditions according to the oil washing rate formula (oil washing rate = (V2 / V1) x 100%), record the experimental data, and observe the influence of different temperatures and salinities on the oil washing rate, so as to determine the adaptability and stability of the bio-based oil displacement gel fracturing fluid system under different temperature and salinity environments, and verify whether the temperature resistance and salt tolerance meet the actual application requirements. The experimental results are shown in Tables 2 and 3.

[0106] Table 2 Static oil washing rate of bio-based oil displacement fracturing fluid gel breaking liquid under different temperatures

[0107]

[0108] Table 3 Static oil washing rate of bio-based oil displacement fracturing fluid gel breaking liquid under different salinities

[0109]

[0110] The experimental results show that the system can effectively reduce the oil-water interfacial tension and significantly improve the oil recovery rate even in an extreme temperature and high salinity environment. Therefore, the present application is particularly suitable for the development of high-temperature and high-salinity reservoirs, effectively solving the problem of performance degradation of traditional fracturing fluids under high-temperature and high-salinity conditions, and providing a new technical guarantee for efficient exploitation under complex reservoir conditions. At the same time, the addition of the bio-based oil displacement agent in the system further enhances the degradation and dispersion capacity of heavy oil components, enabling the system to exhibit excellent oil displacement effect under different reservoir conditions and significantly improving the economic benefits and environmental friendliness of oil production.

[0111] In the field test of the bio-based oil displacement gel fracturing fluid, the reservoir temperature of the test well was 101°C. In order to minimize the damage caused by reservoir reconstruction measures, a low-concentration guanidine gum fracturing fluid system was selected. According to the reservoir characteristics and formation temperature of the well, the corresponding system formula was determined through indoor evaluation and optimization, and 200m 3 The bio-based oil displacement gel fracturing fluid for field application was prepared according to the ratio of Example 4. The viscosity of the guanidine gum base fluid was 33mPa·s, and after adding 2% bio-based oil displacement agent, the viscosity of the base fluid remained 33mPa·s, the viscosity change rate was 0, the initial crosslinking time was 25 seconds, and the gel could be hung after 72 seconds. The liquid performance was stable as a whole. During the fracturing construction process of the test well, 100m 3 The bio-based oil displacement gel fracturing fluid was prepared. After the fracturing construction was completed, the well was treated for 15 days, and then the 2mm oil nozzle was installed the next day for flowback. After 1 day of flowback, the oil pressure stabilized at 16.5MPa, the casing pressure was 17MPa, the daily liquid production reached 45m³, the daily oil production was 1.64 tons / day, and the highest daily oil production could reach 1.81 tons / day. This is in sharp contrast to the maximum daily production of only 0.1 tons / day when the adjacent well was tested, and the oil production and production increase effect is remarkable (see Figure 4 、 5 ).

[0112] The above results show that the bio-based oil displacement gel fracturing fluid system of the present application can exhibit excellent oil displacement performance under reservoir conditions, effectively improve the recovery efficiency of remaining oil, and reduce the damage to the reservoir and environmental pollution, providing an innovative solution for the development of oil production technology and promoting the progress and practical application of bio-oil production technology.

[0113] The examples of the specific embodiments are the preferred embodiments of the present application, but do not limit the protection scope of the present application, so that: any equivalent changes made in accordance with the structure, shape, principle of the present application should be covered within the protection scope of the present application.

Claims

1. A biobased oil-displacing gel fracturing fluid system, characterized in that: The components include the following weight parts: guanidium gel thickening agent 0.25-0.45 parts, anti-swelling agent 0.15-0.35 parts, cleanup agent 0.15-0.35 parts, pH regulator 0.05-0.15 parts, crosslinking agent 0.15-0.35 parts, bio-based oil displacement agent 0.5-3 parts, synergist 0.5-1.5 parts, gel breaker 0.05-0.15 parts, and water 100 parts; The preparation method of the bio-based oil displacement agent is: The Bacillus subtilis BZ-1 strain is activated in LB medium, a single colony is picked and inoculated in LB liquid medium, and cultured at 35-40 DEG C, 180-200 rpm for 12-24 h; the inoculation amount is 1%, and the culture is transferred to LB liquid medium and cultured at 35-40 DEG C, 180-200 rpm until the OD600 is 0.5-0.8; then the inoculation amount is 5%, and the culture is transferred to a shake flask containing fermentation medium and cultured at 35-40 DEG C, 180-200 rpm for 24-48 h; the inoculation amount is 5%, and the culture is transferred to a fermentation tank containing fermentation medium and fermented at 35-40 DEG C for 48-72 h; the fermentation liquid is preliminarily filtered, the obtained filtrate is broken wall treated and then finely filtered, and then compounded with decyl alkyl hydroxypropyl sulfobetaine, fatty alcohol polyoxyethylene ether ammonium sulfate at a mass ratio of 10:2:1 to obtain the bio-based oil displacement agent. The Bacillus subtilis BZ-1 has been preserved in the China General Microbiological Culture Collection Center on November 15, 2024, and the preservation number is CGMCC No. 32653.

2. The biobased oil-displacing gel fracturing fluid system according to claim 1, characterized in that: The fermentation medium includes the following weight parts of components: glucose 5 parts, sodium acetate 5 parts, ammonium sulfate 1 part, dipotassium hydrogen phosphate 4.8 parts, potassium dihydrogen phosphate 1.5 parts, trisodium citrate 0.5 parts, magnesium sulfate 0.5 parts, yeast extract 0.2 parts, calcium carbonate 0.01 parts, manganese sulfate 0.002 parts, ferrous sulfate 0.1 parts, nickel chloride 0.0004 parts, zinc sulfate 0.0004 parts, ferric chloride 0.0002 parts, sodium molybdate 0.0002 parts, and distilled water to 1000 parts.

3. The biobased oil-displacing gel fracturing fluid system according to claim 1, characterized in that: The guanidium gel thickening agent is one or more of guar gum, hydroxypropyl guar gum, and carboxymethyl guar gum.

4. The biobased oil-displacing gel fracturing fluid system according to claim 1, characterized in that: The anti-swelling agent is selected from one or more of potassium chloride, ammonium chloride, and potassium sulfate.

5. The biobased oil-displacing gel fracturing fluid system according to claim 1, characterized in that: The cleanup agent is selected from one or more of dodecyl dimethyl betaine, fatty alcohol polyoxyethylene ether, and sodium dodecyl benzene sulfonate.

6. The biobased oil-displacing gel fracturing fluid system of claim 1, wherein: The crosslinking agent is selected from one or more of tetrabutyl titanate, zirconium oxychloride octahydrate, and boric acid triethanolamine complex.

7. The biobased oil-displacing gel fracturing fluid system according to claim 1, characterized in that: The synergist includes the following weight parts of components: 5-10 parts of lipopeptide, 5-10 parts of rhamnolipid, and distilled water to 1000 parts.

8. The biobased oil-displacing gel fracturing fluid system of claim 1, wherein: The pH regulator is selected from one or more of sodium carbonate, sodium hydroxide, and potassium hydroxide; and the gel breaker is one or more of ammonium persulfate and potassium persulfate.

9. A method of preparing the bio-based oil displacement gel fracturing fluid system according to any one of claims 1-8, characterized in that: The method includes the following steps: S1. A prescribed amount of guanidium gel thickening agent, anti-swelling agent, cleanup agent, and pH regulator is added to water in sequence while stirring, and mixed and swelled to obtain a raw gel solution; S2. A certain amount of lipopeptide is added into an alkaline aqueous solution with pH 9.0-10.0 to form a dispersion under stirring, then rhamnolipid is added, and the mixture is mechanically stirred at room temperature for 1-2 h to obtain the synergist; S3. The crosslinking agent, the bio-based oil displacement agent, the synergist and the gel breaker are sequentially added into the original gel solution, and the mixture is stirred uniformly to obtain the bio-based oil displacement gel fracturing fluid system.

Images