A method for managing hydrogen sulfide in oil wells

Abstract

The application discloses a method for treating hydrogen sulfide in oil wells, which comprises the following steps: (1) screening of test oil reservoir; (2) preparation of specific virulent SRB phage stock solution; (3) enrichment of specific virulent SRB phage; (4) determination of optimal titer of specific virulent SRB phage solution; (5) selection of phage fusion bactericide; (6) determination of optimal intervention point of bactericide; (7) field test and effect evaluation. The application has the following advantages: (1) wide adaptability, simple method and good operability; (2) strong pertinence; (3) phage bactericidal action can prevent the generation of bacterial drug resistance and can prolong the use time of bactericide; (4) the cost is reduced by more than 50% compared with the prior art; meanwhile, the damage of bactericide toxicity to the formation is reduced, and the method is economic and environment-friendly.

Description

Technical Field

[0001] This invention relates to the field of microbial control technology in oilfield systems. Specifically, this invention discloses a method for treating hydrogen sulfide in oil wells. Background Technology

[0002] Sulfate-reducing bacteria (SRB) are a type of organism that can convert SO42- into sulfur dioxide. 2- SRB (Self-Reducing Bacteria) is a collective term for bacteria that reduce H2S to oxygen and obtain energy from it. It is a type of anaerobic microorganism that feeds on organic matter and is widely found in oxygen-deficient environments such as soil, seawater, silt, underground pipelines, and oil and gas wells with a pH of 6-9. SRB are prevalent in all aspects of oilfield systems. Statistics show that over 70% of H2S generated in domestic and international oilfield systems is caused by SRB. It can lead to microbial corrosion, water quality deterioration, reduced polymer viscosity, and harm to human health, seriously affecting safe oilfield production and causing environmental damage and economic losses.

[0003] Currently, the main sterilization technologies for SRB (sulfate-reducing bacteria) include physical methods, chemical methods, and biological control methods. Physical methods often utilize cathodic protection, ultraviolet and ultrasonic sterilization, and high-pressure pulse sterilization technologies. For example, Chinese invention patent application CN106542622 A discloses a device for treating sulfate-reducing bacteria in oilfield produced fluid using magnetic fields and ultrasound. This device includes metal fittings, copper pipes, an ultrasonic generator, a transducer, and a coil. The metal fittings are connected to the oilfield produced fluid delivery pipeline. The transducer is located outside the metal fittings and is tightly connected to the outer diameter of the metal fittings. The ultrasonic generator is connected to the transducer. The copper pipe is located outside the metal fittings, and its inner diameter is tightly connected to the outer diameter of the metal fittings. The coil is wound around the outside of the copper pipe. However, physical methods are difficult to operate and have high economic costs, making them unsuitable for field use in oilfields. Chemical methods mainly refer to the application of bactericides, which are widely used in oil fields. The bactericides used in domestic oil fields are mainly quaternary ammonium salts. For example, Chinese invention patent application CN103168775 A discloses a double quaternary ammonium salt type gas field reinjection water bactericide and a bactericidal composition containing the above-mentioned bactericide. The double quaternary ammonium salt of this invention has a higher positive charge density than the traditional bactericide 1227, increasing its ability to adsorb negatively charged bacterial cell surfaces, thus exhibiting strong bactericidal activity, a long duration of effect, and less foaming. The double long-chain quaternary ammonium salt has one hydrophilic group and two lipophilic groups, giving it a stronger ability to reduce surface tension and enhance water solubility, exhibiting excellent solubility and stability even in water with high hardness. Using the aforementioned bactericidal composition for gas field reinjection water, bacterial testing was conducted according to the erasure dilution method described in SY / T0532-93. Bactericidal experiments were performed against sulfate-reducing bacteria (SRB), iron bacteria (FB), and saprophytic bacteria (TGB). The effective bactericidal concentration was 20-30 ppm, with a bactericidal rate exceeding 99.9%, meeting reinjection requirements. However, long-term use of bactericides can lead to SRB resistance, resulting in increased dosage. Furthermore, the high toxicity of chemical agents can cause environmental pollution. Improving the bactericidal efficiency and reducing the dosage of bactericides are urgent problems to be solved. Biological control, which utilizes the symbiotic, competitive, and antagonistic relationships between microorganisms to control harmful microorganisms, is a green, environmentally friendly, economical, and efficient sterilization method.

[0004] Chinese invention patent application CN101229943 A discloses a method for controlling hydrogen sulfide by enhancing the activity of endogenous microorganisms. This method utilizes the activation of nitrate-reducing bacteria in oilfield water to competitively inhibit the growth of SRB bacteria, thereby controlling hydrogen sulfide. However, this method only works for water samples containing nitrate-reducing bacteria, and the biological competition can only suppress SRB bacteria to a certain level. Once SRB bacteria develop resistance, there is a risk of their numbers rapidly recovering, increasing the difficulty of subsequent treatment.

[0005] Currently, utilizing bacteriophages for sterilization is a new research direction in biocontrol. Bacteriophages, also known as bacterial viruses, are viruses widely found in nature. Virulent bacteriophages can specifically invade the "host" bacterial cells, replicate and multiply within the host cells, producing progeny bacteriophages exponentially. They then destroy the cell wall through enzymatic action, causing bacterial lysis and killing the bacteria through "bacteriolysis." Utilizing bacteriophages for sterilization is a research approach for the biocontrol of SRB and the inhibition of H2S in oil wells, offering advantages such as high specificity, strong reproductive capacity, and no development of drug resistance.

[0006] Chinese invention patent CN109439305 B discloses a method for improving the viscosity stability of polymer solutions. Specifically, it includes the isolation and screening of sulfate-reducing bacteriophages (SRBs), and by inhibiting SRBs, reducing the content of sulfides produced by their metabolism, thereby ensuring the viscosity of the polymer. This effectively solves the problem of viscosity loss caused by sulfides produced by SRBs during the transportation of polymer solutions in oil fields.

[0007] Chinese invention patent CN111119818 B discloses a method for targeted regulation of endogenous functional microorganisms in oil reservoirs, which also includes the isolation and screening of sulfate-reducing bacteriophages. Through the screening of targeted activation systems, the endogenous functional microorganisms in oil reservoirs are targeted and regulated. This is a method for inhibiting SRB and activating other functional bacteria.

[0008] Both patents mentioned above involve the screening and isolation of SRB phages, but they fail to effectively evaluate and optimize the efficacy of SRB phages, meaning the obtained SRB phages may not be in their optimal state or at the optimal concentration. Furthermore, literature review indicates that using phages alone achieves approximately 90% bactericidal efficacy, controlling SRB numbers to a low level but not completely eliminating them. Currently, the highest bactericidal efficiency of bactericides used in oilfields reaches 90%, but the use of bactericides easily leads to SRB resistance, gradually reducing bactericidal efficiency. Biological competitive inhibition, the use of phages alone, and the use of bactericides alone cannot achieve complete sterilization, and SRBs will rapidly proliferate again in the short term after application. Therefore, there is an urgent need for a method that can completely eliminate SRB bacteria in oil wells. Summary of the Invention

[0009] Objective: This invention addresses the root cause of H2S production in oil wells—sulfate-reducing bacteria (SRB)—by providing a method for controlling H2S in oil wells. The invention provides a method for isolating and determining the optimal titer of a specific, highly virulent bacteriophage targeting SRB. Furthermore, it specifically fuses the specific highly virulent bacteriophage with a bactericide to further enhance the bactericidal effect. This invention can effectively control H2S in oil wells, significantly reduce the amount of bactericide used, reduce formation damage, and simultaneously reduce costs by more than 50%.

[0010] Technical solution: A method for treating hydrogen sulfide in oil wells, comprising the following steps:

[0011] (1) Screening of test reservoirs;

[0012] (2) Preparation of specific virulent SRB phage stock solution;

[0013] (3) Enrichment of obligate virulent SRB phages;

[0014] (4) Determine the optimal titer of the obligate virulent SRB phage liquid;

[0015] (5) Selection of bacteriophage fusion bactericides;

[0016] (6) Determining the optimal intervention point for the use of bactericides;

[0017] (7) Field test and effect evaluation.

[0018] Furthermore, the screening conditions for the test reservoir in step (1) are as follows: H2S wellhead concentration > 10 ppm, and the concentration of sulfate-reducing bacteria in the reservoir water sample > 25 cells / ml.

[0019] Furthermore, the sulfate-reducing bacteria are *Desulfovibrio* spp. Desulfovibrio ), Desulfomonas spp. Desulfomonas ), Desulfococcus spp. Desulfococcus ), Desulfobacterium spp. Desulfobacter ), Desulfurized Leaf Fungus ( Desulfobullbus ), Desulfurized Onion Bacteria ( Desulfobulbus ), Desulfurized Enterobacteriaceae ( Desulfotomaculum One or more of the following.

[0020] Furthermore, the specific steps of step (2) are as follows:

[0021] (21) Take at least 3L of produced water from the well in the test reservoir, let it stand in a sealed room for at least 36 hours until the oil and water separate, take 1L of the water sample from the bottom, centrifuge it at 10000-12000RPM for 15-30 minutes to remove solid impurities, and collect the supernatant.

[0022] (22) Filter the supernatant using a cellulose filter membrane: First, add 50-100 mL of autoclaved sulfate-reducing bacteria culture medium to the anaerobic bottle, then add 50-100 mL of the supernatant, then inoculate with 5-10 mL of experimental reservoir sulfate-reducing bacteria culture medium cultured indoors, mix well, remove the air from the anaerobic bottle with a vacuum pump, then purge with nitrogen or inert gas, perform at least 4 cycles to reach the anaerobic environment, seal, let stand at room temperature for at least 30 minutes, then place the anaerobic bottle in a constant temperature incubator and incubate at the reservoir temperature for at least 24 hours; after centrifugation at 10000-12000 RPM for 15-30 minutes, collect the supernatant, and then filter the centrifuged supernatant through a cellulose filter membrane to obtain the filtrate, which is the obligate virulent SRB phage stock solution.

[0023] Furthermore, the pore size of the cellulose filter membrane in step (22) is no greater than 0.22 μm, preferably 0.22 μm.

[0024] Furthermore, the preparation steps of the sulfate-reducing bacteria culture medium are as follows: Dissolve 0.5-1g of yeast extract, 0.3-0.5g of dipotassium hydrogen phosphate, 1.0-1.5g of ammonium chloride, 0.1-0.5g of anhydrous calcium chloride, 2.0-3.0g of magnesium sulfate heptahydrate, 0.5-1.0g of ferrous sulfate heptahydrate, 1.0-1.5g of sodium chloride, 0.3-0.5g of ascorbic acid, 0.3-0.5g of L-cyscysteine, 3-5g of anhydrous sodium sulfate, and 3.0-5.0g of sodium lactate in 1L of water, adjust the pH to 6.5-7.0, and obtain the sulfate-reducing bacteria culture medium after complete dissolution.

[0025] Furthermore, the preparation steps of the culture medium for sulfate-reducing bacteria in the experimental oil reservoir cultured indoors are as follows:

[0026] Dissolve 0.5-1g of yeast extract, 0.3-0.5g of dipotassium hydrogen phosphate, 1.0-1.5g of ammonium chloride, 0.1-0.5g of anhydrous calcium chloride, 2.0-3.0g of magnesium sulfate heptahydrate, 0.5-1.0g of ferrous sulfate heptahydrate, 1.0-1.5g of sodium chloride, 0.3-0.5g of ascorbic acid, 0.3-0.5g of L-cyscysteine, 3-5g of anhydrous sodium sulfate, and 3.0-5.0g of sodium lactate in 1L of produced fluid from the well in the test reservoir. After complete dissolution, remove the air from the culture bottle using a vacuum pump, then purge with nitrogen for at least 4 cycles before sealing. Place the anaerobic bottle in a constant temperature incubator and incubate at the reservoir temperature for at least 7 days to obtain the culture medium for sulfate-reducing bacteria in the test reservoir culture.

[0027] Furthermore, the specific steps of step (3) are as follows:

[0028] Take 10-20 mL of the above-mentioned obligate virulent SRB phage stock solution and inoculate it into 1-2 L of sulfate-reducing bacteria culture medium in the test reservoir that has reached the logarithmic growth phase for large-scale culture. After culturing at the test reservoir temperature until the sulfate-reducing bacteria culture medium in the test reservoir becomes clear, centrifuge and filter to collect the filtrate to obtain the obligate virulent SRB phage. After freeze-drying, obtain the obligate virulent SRB phage dry powder and store it at -4℃.

[0029] Furthermore, the specific steps of step (4) are as follows:

[0030] Inoculate 0.1-0.3 wt% of the described obligate virulent SRB phage dry powder into five 1 L portions of sulfate-reducing bacteria culture medium that has reached the logarithmic growth phase in the test reservoir. Incubate at reservoir temperature for 6, 8, 10, 12, and 15 days respectively. Take 10 ml of the cultured phage and add it to 1 L of sulfate-reducing bacteria culture medium that has reached the logarithmic growth phase in the test reservoir. Monitor the H2S concentration in the anaerobic bottle. The optimal titer of the obligate virulent SRB phage liquid is determined by the number of days the phage and sulfate-reducing bacteria co-cultured for the longest time can inhibit H2S.

[0031] Furthermore, the specific steps of step (5) are as follows:

[0032] Five 10ml portions of the optimal potency of obligate virulent SRB phage determined in step (4) were added to five 1L portions of sulfate-reducing bacteria culture medium from the test reservoir that had reached the logarithmic growth phase, along with 10ml of THPS aqueous solution, 10ml of 1227 aqueous solution, 10ml of S-29 aqueous solution, 10ml of KSG aqueous solution, and 10ml of SJT aqueous solution, respectively. The mixtures were incubated at reservoir temperature, and the H2S concentration in the anaerobic flasks was monitored to determine the most suitable bactericide.

[0033] The concentrations of the following fungicides were 50 mg / L: THPS aqueous solution, 10 ml of 1227 aqueous solution, 10 ml of S-29 aqueous solution, 10 ml of KSG aqueous solution, and 10 ml of SJT aqueous solution.

[0034] Furthermore, after determining the type of bactericide, 10 ml of the optimal potency of the obligate virulent SRB bacteriophage determined in step (4) and 10 ml of bactericide aqueous solutions of different concentrations were added to 1 L of sulfate-reducing bacteria culture medium in the test reservoir that had reached the logarithmic growth phase. The culture was carried out at the reservoir temperature, and the H2S concentration in the anaerobic bottle was monitored to determine the optimal bactericide concentration, wherein:

[0035] The concentration range for the bactericide is 10 mg / L to 50 mg / L.

[0036] Further, step (6) includes the following steps: optimal titer of obligate virulent SRB phage liquid.

[0037] Ten 10ml portions of obligate virulent SRB phage cultured to their optimal titer were added to 1L of sulfate-reducing bacteria culture medium in the experimental reservoir that had reached the logarithmic growth phase. After co-culturing for 1, 2, 3, 4, 5, 6, 7, 8, 9, and 10 days, the optimal concentration of the optimal bactericide was added, and the mixture was incubated at the reservoir temperature. The H2S concentration in the anaerobic flask was monitored.

[0038] The longest period of time that H2S can be suppressed to <2 mg / L before the addition of bactericide is the optimal intervention point for bactericide.

[0039] Furthermore, step (7) includes the following steps:

[0040] The optimal potency of the specific potent SRB bacteriophage and the optimal type and concentration of bactericide were added to the joint station corresponding to the test reservoir at a rate of 0.2-0.5 PV, following the order of adding the bacteriophage first and then the bactericide at the optimal intervention point. At the same time, the H2S concentration was monitored at the wellhead of the corresponding oil well to evaluate the effect.

[0041] Beneficial effects: The method for controlling hydrogen sulfide in oil wells disclosed in this invention uses a specific and potent SRB bacteriophage fusion bactericide to control H2S in oil wells, which has the following advantages compared with the prior art:

[0042] (1) It has a wide range of applications. This invention is applicable to the vast majority of oil wells with H2S problems. The method is simple and easy to operate.

[0043] (2) It is highly targeted. This invention screens specific and virulent SRB phages and determines the titer of the optimal phage to inhibit the growth of SRB in oil wells and achieve the purpose of inhibiting H2S. It can effectively regulate harmful SRB bacteria in oil reservoirs and achieve long-term inhibition of H2S.

[0044] (3) Using bacteriophages to kill bacteria can prevent the development of bacterial resistance and extend the service life of bactericides;

[0045] (4) The effective fusion of bacteriophages with bactericides to inhibit SRB can increase the bactericidal effect and reduce the amount of bactericide used by 70%, reducing costs by more than 50% compared with existing methods; at the same time, it reduces the damage of bactericide toxicity to the formation, making it economical and environmentally friendly. Attached Figure Description

[0046] Figure 1 This is a schematic diagram illustrating the effect of co-culturing bacteriophage and SRB for different number of days in Example 1 on inhibiting hydrogen sulfide.

[0047] Figure 2This is a schematic diagram illustrating the effect of bacteriophage fusion with different types of bactericides on inhibiting hydrogen sulfide in the examples.

[0048] Figure 3 This is a schematic diagram illustrating the effect of different concentrations of THPS on inhibiting hydrogen sulfide in Example 1.

[0049] Figure 4 This is a schematic diagram illustrating the effect of co-culturing bacteriophage and SRB for different number of days in Example 2 on inhibiting hydrogen sulfide.

[0050] Figure 5 This is a schematic diagram illustrating the effect of bacteriophage fusion with different types of bactericides on inhibiting hydrogen sulfide in Example 2.

[0051] Figure 6 This is a schematic diagram illustrating the effect of different concentrations of KSG on inhibiting hydrogen sulfide in Example 2.

[0052] Figure 7 This is a schematic diagram illustrating the effect of co-culturing bacteriophage and SRB for different number of days in Example 3 on inhibiting hydrogen sulfide.

[0053] Figure 8 This is a schematic diagram illustrating the effect of bacteriophage fusion with different types of bactericides in inhibiting hydrogen sulfide in Example 3.

[0054] Figure 9 This is a schematic diagram illustrating the effect of different concentrations of SJT in inhibiting hydrogen sulfide in Example 3.

[0055] Figure 10 This is a flowchart of a method for treating hydrogen sulfide in oil wells disclosed in this invention. Detailed Implementation

[0056] The specific embodiments of the present invention are described in detail below.

[0057] Example 1

[0058] Test Block C of a certain oil production plant in Shengli Oilfield 13 In well A, the H2S concentration at the wellhead is 320ppm, the SRB number is 120 / ml, and the reservoir temperature is 52℃. The original H2S treatment plan was to periodically add bactericide 1227.

[0059] The method of this invention is used to prevent and control H2S.

[0060] A method for treating hydrogen sulfide in oil wells, comprising the following specific steps:

[0061] (1) Screening of test reservoirs;

[0062] Oil well A meets the screening criteria for the experimental reservoir, with an H2S wellhead concentration >10ppm and a sulfate-reducing bacteria concentration >25 CFU / ml in the reservoir water sample.

[0063] Wherein: the sulfate-reducing bacteria are *Vibrio desulfuriformes*. In another embodiment, the sulfate-reducing bacteria are *Desulfomonas*. Desulfomonas In another embodiment, the sulfate-reducing bacteria is *Desulfococcus* ( ). Desulfococcus In another embodiment, the sulfate-reducing bacteria is *Desulfobacterium* ( ). Desulfobacter In another embodiment, the sulfate-reducing bacteria is a species of *Desulfurobacterium* (…). Desulfobullbus In another embodiment, the sulfate-reducing bacteria is *Desulfuronium* (genus *Onionella*). Desulfobulbus In another embodiment, the sulfate-reducing bacteria are *Enterobacter* spp. (…). Desulfotomaculum In another embodiment, the sulfate-reducing bacteria include *Desulfovibrio* (*Vibrio* spp.). Desulfovibrio ), Desulfomonas spp. Desulfomonas ), Desulfococcus spp. Desulfococcus ), Desulfobacterium spp. Desulfobacter ), Desulfurized Leaf Fungus ( Desulfobullbus ), Desulfurized Onion Bacteria ( Desulfobulbus ), Desulfurized Enterobacteriaceae ( Desulfotomaculum ).

[0064] (2) Preparation of specific virulent SRB phage stock solution;

[0065] (21) Take 4L of produced water from the oil well, let it stand in a sealed room for 42 hours until the oil and water separate into layers, take 1L of the water sample, centrifuge it at 11000RPM for 20 minutes to remove solid impurities, and collect the supernatant.

[0066] (22) Filtering the supernatant using a 0.22μm cellulose membrane: Add 75mL of autoclaved sulfate-reducing bacteria culture medium to the anaerobic bottle, then add 75mL of the supernatant, inoculate with 7.5mL of experimental reservoir sulfate-reducing bacteria culture medium cultured indoors, mix well, remove the air from the anaerobic bottle with a vacuum pump, then purge with nitrogen, perform 5 cycles to reach the anaerobic environment, seal, let stand at room temperature for 40 minutes, then place the anaerobic bottle in a constant temperature incubator and incubate at 52℃ for 36h; after centrifugation at 11000RPM for 20 minutes, collect the supernatant, then filter the centrifuged supernatant through a 0.22μm cellulose membrane, and the obtained filtrate is the obligate virulent SRB phage stock solution.

[0067] The specific steps for preparing the sulfate-reducing bacteria culture medium are as follows: Dissolve 1g of yeast extract, 0.5g of dipotassium hydrogen phosphate, 1.5g of ammonium chloride, 0.5g of anhydrous calcium chloride, 2.5g of magnesium sulfate heptahydrate, 1g of ferrous sulfate heptahydrate, 1.5g of sodium chloride, 0.3g of ascorbic acid, 0.3g of L-cyscysteine, 3.5g of anhydrous sodium sulfate, and 5g of sodium lactate in 1L of water and adjust the pH to 6.9.

[0068] The specific steps for preparing the culture medium of sulfate-reducing bacteria in the experimental oil reservoir for indoor culture are as follows: Dissolve 1g of yeast extract, 0.5g of dipotassium hydrogen phosphate, 1.5g of ammonium chloride, 0.5g of anhydrous calcium chloride, 2.5g of magnesium sulfate heptahydrate, 1g of ferrous sulfate heptahydrate, 1.5g of sodium chloride, 0.3g of ascorbic acid, 0.3g of L-cyscysteine, 3.5g of anhydrous sodium sulfate, and 5g of sodium lactate in 1L of produced fluid from an oil well. After complete dissolution, remove the air from the culture bottle using a vacuum pump, purge with nitrogen for 5 cycles, seal, and place the anaerobic bottle in a constant temperature incubator. Culture at 52℃ for 10 days to obtain the culture medium.

[0069] (3) Enrichment of obligate virulent SRB phages

[0070] Take 15 mL of the above-mentioned obligate virulent SRB phage stock solution and inoculate it into 1.5 L of sulfate-reducing bacteria culture medium that has reached the logarithmic growth phase in the test reservoir for expansion culture. After culturing at 52℃ until the sulfate-reducing bacteria culture medium in the test reservoir becomes clear, centrifuge and filter to collect the filtrate to obtain the obligate virulent SRB phage. After freeze-drying, store the obligate virulent SRB phage powder at -4℃ for later use.

[0071] (4) Determine the optimal titer of the obligate virulent SRB phage liquid.

[0072] Five 1L portions of 1L sulfate-reducing bacteria culture medium from experimental oil reservoirs that had reached the logarithmic growth phase were inoculated with 0.2% of the above-mentioned obligate virulent SRB phage dry powder. The phages were cultured at 52℃ for 6, 8, 10, 12, and 15 days, respectively. 10ml of the cultured phage was then added to 1L of the logarithmic growth phase sulfate-reducing bacteria culture medium from the experimental oil reservoirs, and the H2S concentration in the anaerobic flasks was monitored. The phages obtained after 10 days of growth showed the best H2S inhibition effect (see...). Figure 1 That is, the optimal titer of the phage liquid is 10 days.

[0073] (5) Selection of bacteriophage fusion bactericides

[0074] Five phages (10 ml each) obtained by co-culturing sulfate-reducing bacteria of the test reservoir for 10 days were added to 1 L of 1 L sulfate-reducing bacteria culture medium that had reached the logarithmic growth phase. The phages were then cultured at 52 °C, and the H2S concentration in the anaerobic flask was monitored (see [link to anaerobic flask]). Figure 2 The most suitable fungicide was determined to be THPS.

[0075] After identifying the species, THPS bactericides at concentrations of 10, 20, 30, 40, and 50 mg / L were added to the sulfate-reducing bacteria culture medium in the test reservoir. The cultures were then cultured and monitored according to the method described above (results are shown in [link to results]). Figure 3 The optimal concentration of the bactericide was determined to be 40 mg / L.

[0076] (6) Determining the optimal intervention point for the use of bactericides

[0077] Ten ml of obligate virulent SRB phage cultured for 10 days was added to 1 L of sulfate-reducing bacteria culture medium from the experimental reservoir that had reached the logarithmic growth phase. The cultures were co-cultured for 1, 2, 3, 4, 5, 6, 7, 8, 9, and 10 days, after which 40 mg / L of THPS was added and the cultures were incubated at 52°C. The H2S concentration in the anaerobic flask was monitored. Adding the bactericide 4 days after phage addition resulted in the longest period of H2S inhibition at <2 mg / L, indicating that the optimal intervention point for the bactericide was 4 days after phage application.

[0078] (7) Field test and effect evaluation

[0079] First, 0.4 PV of obligate virulent SRB bacteriophage co-cultured for 10 days was added to the joint station corresponding to the test reservoir. After 4 days, 0.3 PV of 40 mg / L THPS bactericide was added. The H2S concentration was monitored at the wellhead of the corresponding oil well. After 5 days, the hydrogen sulfide concentration was reduced from 320 ppm to 0 ppm. The measures were effective, and the method of the present invention reduced the cost by 53.2% compared with the existing methods.

[0080] Example 2

[0081] In a test block Z2 of a certain oil production plant in Shengli Oilfield, well B had an H2S concentration of 150 ppm at the wellhead, an SRB count of 50 per ml, and a reservoir temperature of 63℃. No H2S treatment was carried out.

[0082] The method of this invention is used to prevent and control H2S.

[0083] A method for treating hydrogen sulfide in oil wells, comprising the following specific steps:

[0084] (1) Screening of test reservoirs;

[0085] Oil well A meets the screening criteria for the experimental reservoir, with an H2S wellhead concentration >10ppm and a sulfate-reducing bacteria concentration >25 CFU / ml in the reservoir water sample.

[0086] The sulfate-reducing bacteria mentioned above include the genus *Desulfomonas*.

[0087] (2) Preparation of specific virulent SRB phage stock solution:

[0088] (21) Take 5L of produced water from the oil well, let it stand in a sealed room for 36 hours until the oil and water separate into layers, take 1L of the water sample, centrifuge it at 10000RPM for 30 minutes to remove solid impurities, and collect the supernatant.

[0089] (22) Filtering the supernatant using a 0.22μm cellulose membrane: First, add 50mL of autoclaved sulfate-reducing bacteria culture medium to the anaerobic bottle, then add 50mL of the supernatant, then inoculate with 5mL of experimental reservoir sulfate-reducing bacteria culture medium cultured indoors, mix well, remove air from the anaerobic bottle using a vacuum pump, then purge with nitrogen, perform 4 cycles to achieve an anaerobic environment, seal, let stand at room temperature for 30 minutes, then place the anaerobic bottle in a constant temperature incubator and incubate at 63℃ for 24h; after centrifugation at 10000RPM for 30 minutes, collect the supernatant, then filter the centrifuged supernatant through a 0.22μm cellulose membrane. The obtained filtrate is the specific virulent SRB phage stock solution, in which:

[0090] The preparation steps of the sulfate-reducing bacteria culture medium are as follows: Dissolve 0.5g of yeast extract, 0.35g of dipotassium hydrogen phosphate, 1.0g of ammonium chloride, 0.1g of anhydrous calcium chloride, 2.0g of magnesium sulfate heptahydrate, 0.6g of ferrous sulfate heptahydrate, 1.2g of sodium chloride, 0.4g of ascorbic acid, 0.4g of L-cyscysteine, 3g of anhydrous sodium sulfate, and 3.5g of sodium lactate in 1L of water and adjust the pH to 7.0.

[0091] The preparation steps of the culture medium for sulfate-reducing bacteria in the experimental reservoir cultured indoors are as follows: 0.5g yeast extract, 0.35g dipotassium hydrogen phosphate, 1.0g ammonium chloride, 0.1g anhydrous calcium chloride, 2.0g magnesium sulfate heptahydrate, 0.6g ferrous sulfate heptahydrate, 1.2g sodium chloride, 0.4g ascorbic acid, 0.4g L-cyscysteine, 3g anhydrous sodium sulfate, and 3.5g sodium lactate were dissolved in 1L of produced fluid from an oil well. After complete dissolution, the air in the culture bottle was removed by vacuum pump, and nitrogen gas was purged for 4 cycles before sealing. The anaerobic bottle was placed in a constant temperature incubator and cultured at 63℃ for 7 days to obtain the culture medium for sulfate-reducing bacteria in the experimental reservoir cultured indoors.

[0092] (3) Enrichment of obligate virulent SRB phages

[0093] Take 10 mL of the above-mentioned obligate virulent SRB phage stock solution and inoculate it into 1 L of sulfate-reducing bacteria culture medium of the test reservoir that has reached the logarithmic growth phase for large-scale culture. After culturing at 63℃ until the sulfate-reducing bacteria culture medium of the test reservoir becomes clear, centrifuge and filter to collect the filtrate to obtain the obligate virulent SRB phage. After freeze-drying, store the obligate virulent SRB phage powder at 4℃ for later use.

[0094] (4) Determine the optimal titer of the obligate virulent SRB phage liquid.

[0095] Five 1L portions of 1L sulfate-reducing bacteria culture medium from experimental oil reservoirs that had reached the logarithmic growth phase were inoculated with 0.1% of the above-mentioned obligate virulent SRB phage dry powder. The phages were cultured at 63℃ for 6, 8, 10, 12, and 15 days, respectively. 10ml of the cultured phage was then added to 1L of the logarithmic growth phase sulfate-reducing bacteria culture medium from the experimental oil reservoirs, and the H2S concentration in the anaerobic flasks was monitored. The phages obtained after 8 days of growth showed the best H2S inhibition effect (see...). Figure 4 That is, the optimal titer of the phage liquid is 8 days.

[0096] (5) Selection of bacteriophage fusion bactericides

[0097] Five 10 ml aliquots of bacteriophages obtained by co-culturing sulfate-reducing bacteria of the test reservoir for 8 days were added simultaneously with 10 ml of 50 mg / L aqueous solutions of THPS, 1227, S-29, KSG, and SJT to 1 L of sulfate-reducing bacteria culture medium that had reached the logarithmic growth phase in the test reservoir. The cultures were incubated at 63°C, and the H2S concentration in the anaerobic flasks was monitored (see...). Figure 5 The most suitable fungicide was determined to be KSG.

[0098] After identifying the species, bactericides KSG at concentrations of 10 mg / L, 20 mg / L, 30 mg / L, 40 mg / L, and 50 mg / L were added to the sulfate-reducing bacteria culture medium in the test reservoir. The culture was then incubated and monitored according to the method described above (see [link to relevant documentation]). Figure 6 The optimal concentration of the bactericide was determined to be 30 mg / L.

[0099] (6) Determining the optimal intervention point for the use of bactericides

[0100] Ten 10ml portions of obligate virulent SRB bacteriophages, cultured for 8 days, were added to 1L of sulfate-reducing bacteria culture medium from the experimental reservoir that had reached the logarithmic growth phase. After co-culturing for 1, 2, 3, 4, 5, 6, 7, 8, 9, and 10 days, 30mg / L of the bactericide KSG was added, and the mixture was incubated at 63℃. The H2S concentration in the anaerobic flask was monitored. Adding the bactericide 8 days after phage administration resulted in the longest period of H2S inhibition at <2mg / L, indicating that the optimal intervention point for the bactericide was 8 days after phage administration.

[0101] (7) Field test and effect evaluation

[0102] First, 0.2 PV of a co-cultured, highly virulent SRB bacteriophage was added to the joint station corresponding to the test reservoir after 8 days. Then, 0.4 PV of 30 mg / L KSG bactericide was added. The H2S concentration was monitored at the wellhead of the corresponding oil well. After 4.5 days, the hydrogen sulfide concentration was reduced from 150 ppm to 0 ppm. The measures were effective, and the method of the present invention reduced the cost by 50.7% compared with the existing methods.

[0103] Example 3

[0104] In a test block Y8 of a certain oil production plant in Shengli Oilfield, well C had an H2S concentration of 1200ppm at the wellhead, an SRB count of 250 cells / ml, and a reservoir temperature of 70℃. The original H2S treatment plan was to periodically add the bactericide THPS.

[0105] The method of this invention is used to prevent and control H2S.

[0106] A method for treating hydrogen sulfide in oil wells, comprising the following specific steps:

[0107] (1) Screening of test reservoirs;

[0108] Oil well A meets the screening criteria for the experimental reservoir, with an H2S wellhead concentration >10ppm and a sulfate-reducing bacteria concentration >25 CFU / ml in the reservoir water sample.

[0109] The sulfate-reducing bacteria mentioned above include the genus *Desulfomonas*.

[0110] (2) Preparation of specific virulent SRB phage stock solution:

[0111] (21) Take 3L of produced water from the oil well, let it stand in a sealed room for 36 hours until the oil and water separate, take 1L of the water sample, centrifuge it at 12000RPM for 15 minutes to remove solid impurities, and collect the supernatant.

[0112] (22) Filtering the supernatant using a 0.22μm cellulose membrane: First, add 100mL of autoclaved sulfate-reducing bacteria culture medium to the anaerobic bottle, then add 00mL of the supernatant, then inoculate with 10mL of experimental reservoir sulfate-reducing bacteria culture medium cultured indoors, mix well, remove air from the anaerobic bottle with a vacuum pump, then purge with nitrogen, perform 6 cycles to achieve an anaerobic environment, seal, let stand at room temperature for 60 minutes, then place the anaerobic bottle in a constant temperature incubator and incubate at 70℃ for 48h; after centrifugation at 12000RPM for 15 minutes, collect the supernatant, then filter the centrifuged supernatant through a 0.22μm cellulose membrane. The obtained filtrate is the specific virulent SRB phage stock solution, in which:

[0113] The preparation steps of the sulfate-reducing bacteria culture medium are as follows: Dissolve 0.7g of yeast extract, 0.4g of dipotassium hydrogen phosphate, 1.2g of ammonium chloride, 0.4g of anhydrous calcium chloride, 3g of magnesium sulfate heptahydrate, 0.5g of ferrous sulfate heptahydrate, 1.0g of sodium chloride, 0.5g of ascorbic acid, 0.5g of L-cyscysteine, 5g of anhydrous sodium sulfate, and 3.0g of sodium lactate in 1L of water and adjust the pH to 6.5.

[0114] The preparation steps of the culture medium for sulfate-reducing bacteria in the experimental reservoir cultured indoors are as follows: 0.7g yeast extract, 0.4g dipotassium hydrogen phosphate, 1.2g ammonium chloride, 0.4g anhydrous calcium chloride, 3g magnesium sulfate heptahydrate, 0.5g ferrous sulfate heptahydrate, 1.0g sodium chloride, 0.5g ascorbic acid, 0.5g L-cyscysteine, 5g anhydrous sodium sulfate, and 3.0g sodium lactate are added to 1L of produced fluid from an oil well. After complete dissolution, the air in the culture bottle is removed by vacuum pump, and nitrogen is purged for 6 cycles before sealing. The anaerobic bottle is placed in a constant temperature incubator and cultured at 70℃ for 14 days to obtain the culture medium for sulfate-reducing bacteria in the experimental reservoir cultured indoors.

[0115] (3) Enrichment of obligate virulent SRB phages

[0116] Take 20 mL of the above-mentioned obligate virulent SRB phage stock solution and inoculate it into 2 L of sulfate-reducing bacteria culture medium in the experimental reservoir that has reached the logarithmic growth phase for expansion culture. After culturing at 70℃ until the sulfate-reducing bacteria culture medium in the experimental reservoir becomes clear, centrifuge and filter to collect the filtrate to obtain the obligate virulent SRB phage. After freeze-drying, store the obligate virulent SRB phage powder at 4℃ for later use.

[0117] (4) Determine the optimal titer of the obligate virulent SRB phage liquid.

[0118] Five 2L portions of 2L sulfate-reducing bacteria culture medium from experimental oil reservoirs that had reached the logarithmic growth phase were inoculated with 0.3% of the above-mentioned obligate virulent SRB phage dry powder. The phages were cultured at 70℃ for 6, 8, 10, 12, and 15 days, respectively. 10ml of the cultured phage was then added to 1L of the logarithmic growth phase sulfate-reducing bacteria culture medium from the experimental oil reservoirs, and the H2S concentration in the anaerobic flasks was monitored. The phages obtained after 6 days of growth showed the best H2S inhibition effect (see...). Figure 7 That is, the optimal titer of the bacteriophage liquid is 6 days.

[0119] (5) Selection of bacteriophage fusion bactericides

[0120] Five 10 ml portions of bacteriophages obtained by co-culturing sulfate-reducing bacteria of the test reservoir for 6 days were added simultaneously to 1 L of sulfate-reducing bacteria culture medium that had reached the logarithmic growth phase, along with 10 ml of 50 mg / L THPS aqueous solution, 10 ml of 1227 aqueous solution, 10 ml of S-29 aqueous solution, 10 ml of KSG aqueous solution, and 10 ml of SJT aqueous solution. The mixtures were incubated at 70 °C, and the H2S concentration in the anaerobic flasks was monitored (see...). Figure 8 The most suitable fungicide was determined to be fungicide SJT.

[0121] After identifying the species, bactericides SJT at concentrations of 10 mg / L, 20 mg / L, 30 mg / L, 40 mg / L, and 50 mg / L were added to the sulfate-reducing bacteria culture medium in the test reservoir. The culture was then incubated and monitored according to the method described above (see [link to relevant documentation]). Figure 9 The optimal concentration of the bactericide was determined to be 20 mg / L.

[0122] (6) Determining the optimal intervention point for the use of bactericides

[0123] Ten 10 ml portions of obligate virulent SRB bacteriophage, cultured for 6 days, were added to 1 L of sulfate-reducing bacteria culture medium from the experimental reservoir that had reached the logarithmic growth phase. After co-culturing for 1, 2, 3, 4, 5, 6, 7, 8, 9, and 10 days, 20 mg / L of the bactericide SJT was added, and the mixture was incubated at 70°C. The H2S concentration in the anaerobic flask was monitored. Adding the bactericide 10 days after phage administration resulted in the longest period of H2S inhibition at <2 mg / L, indicating that the optimal intervention point for the bactericide was 10 days after phage administration.

[0124] (7) Field test and effect evaluation

[0125] First, 0.5 PV of a co-cultured, highly virulent SRB bacteriophage was added to the joint station corresponding to the test reservoir after 6 days. After 10 days, 0.25 PV of 20 mg / L SJT bactericide was added. The H2S concentration was monitored at the wellhead of the corresponding oil well. After 3 days, the hydrogen sulfide concentration was reduced from 1200 ppm to 0 ppm. The measures were effective, and the method of the present invention reduced the cost by 58.3% compared with the existing methods.

[0126] The embodiments of the present invention have been described in detail above. However, the present invention is not limited to the above embodiments, and various changes can be made within the scope of knowledge possessed by those skilled in the art without departing from the spirit of the present invention.

Claims

1. A method for treating hydrogen sulfide in oil wells, characterized in that, Includes the following steps: (1) Screening of test reservoirs. The screening conditions for the test reservoirs are as follows: H2S wellhead concentration > 10 ppm, and the concentration of sulfate-reducing bacteria in the reservoir water sample > 25 cells / ml. (2) Preparation of specific virulent SRB phage stock solution: (21) Take at least 3L of produced water from the well in the test reservoir, let it stand in a sealed room for at least 36 hours until the oil and water separate, take 1L of the water sample from the bottom, centrifuge it at 10000-12000RPM for 15-30 minutes to remove solid impurities, and collect the supernatant. (22) Filter the supernatant using a cellulose filter membrane: First, add 50-100 mL of autoclaved sulfate-reducing bacteria culture medium to the anaerobic bottle, then add 50-100 mL of the supernatant, then inoculate with 5-10 mL of test reservoir sulfate-reducing bacteria culture medium cultured indoors, mix well, remove the air from the anaerobic bottle with a vacuum pump, then purge with nitrogen or inert gas, perform at least 4 cycles to reach the anaerobic environment, seal, let stand at room temperature for at least 30 minutes, then place the anaerobic bottle in a constant temperature incubator and incubate at the reservoir temperature for at least 24 hours; after centrifugation at 10000-12000 RPM for 15-30 minutes, collect the supernatant, then filter the centrifuged supernatant through a cellulose filter membrane to obtain the filtrate, which is the obligate virulent SRB phage stock solution; (3) Enrichment of obligate virulent SRB phages: Take 10-20 mL of the above-mentioned obligate virulent SRB phage stock solution and inoculate it into 1-2 L of sulfate-reducing bacteria culture medium in the test reservoir that has reached the logarithmic growth phase for large-scale culture. After culturing at the test reservoir temperature until the sulfate-reducing bacteria culture medium in the test reservoir becomes clear, centrifuge and filter to collect the filtrate to obtain the obligate virulent SRB phage. After freeze-drying, obtain the obligate virulent SRB phage dry powder and store it at -4℃. (4) Determine the optimal titer of the obligate virulent SRB phage liquid: 0.1-0.3 wt% of the described obligate virulent SRB phage dry powder was inoculated into five 1 L portions of sulfate-reducing bacteria culture medium that had reached the logarithmic growth phase in the test reservoir. The phages were cultured at reservoir temperature for 6, 8, 10, 12, and 15 days, respectively. 10 ml of the cultured phages was then added to 1 L of sulfate-reducing bacteria culture medium that had reached the logarithmic growth phase in the test reservoir. The H2S concentration in the anaerobic bottle was monitored. The optimal titer of the obligate virulent SRB phage liquid was determined by the number of days the phage and sulfate-reducing bacteria co-cultured for the longest time could inhibit H2S. (5) Selection of bacteriophage fusion bactericides: Five 10ml portions of the optimal potency of obligate virulent SRB phage determined in step (4) were added to five 1L portions of sulfate-reducing bacteria culture medium from the test reservoir that had reached the logarithmic growth phase, along with 10ml of THPS aqueous solution, 10ml of 1227 aqueous solution, 10ml of S-29 aqueous solution, 10ml of KSG aqueous solution, and 10ml of SJT aqueous solution, respectively. The mixtures were incubated at reservoir temperature, and the H2S concentration in the anaerobic flasks was monitored to determine the most suitable bactericide. The concentrations of THPS aqueous solution, 10 ml of 1227 aqueous solution, 10 ml of S-29 aqueous solution, 10 ml of KSG aqueous solution, and 10 ml of SJT aqueous solution are all 50 mg / L. After determining the type of bactericide, 10 ml of the optimal potency of the obligate virulent SRB bacteriophage determined in step (4) and 10 ml of bactericide aqueous solutions of different concentrations were added to 1 L of sulfate-reducing bacteria culture medium in the test reservoir that had reached the logarithmic growth phase. The culture was carried out at the reservoir temperature, and the H2S concentration in the anaerobic bottle was monitored to determine the optimal bactericide concentration, wherein: The concentration range for the bactericide is 10 mg / L - 50 mg / L; (6) Determining the optimal intervention point for the use of bactericides: Ten 10ml portions of obligate virulent SRB phage cultured to their optimal titer were added to 1L of sulfate-reducing bacteria culture medium in the experimental reservoir that had reached the logarithmic growth phase. After co-culturing for 1, 2, 3, 4, 5, 6, 7, 8, 9, and 10 days, the optimal concentration of the optimal bactericide was added, and the mixture was incubated at the reservoir temperature. The H2S concentration in the anaerobic flask was monitored. The longest number of days that can suppress H2S to <2 mg / L before adding bactericide is the optimal intervention point for bactericide; (7) Field test and effect evaluation: The optimal potency of the specific potent SRB bacteriophage and the optimal type and concentration of bactericide were added to the joint station corresponding to the test reservoir at a rate of 0.2-0.5 PV, following the order of adding the bacteriophage first and then the bactericide at the optimal intervention point. At the same time, the H2S concentration was monitored at the wellhead of the corresponding oil well to evaluate the effect.

2. The method for treating hydrogen sulfide in oil wells as described in claim 1, characterized in that, The sulfate-reducing bacteria mentioned are one or more of the following genera: *Desulfovibrio*, *Desulfomonas*, *Desulfococcus*, *Desulfobacterium*, *Desulfophyllum*, *Desulfophyllum*, *Desulfophyllum*, and *Desulfoenterobacter*.

3. The method for treating hydrogen sulfide in oil wells as described in claim 1, characterized in that, The pore size of the cellulose filter membrane described in step (22) is no greater than 0.22 μm.

4. The method for treating hydrogen sulfide in oil wells as described in claim 3, characterized in that, The pore size of the cellulose filter membrane in step (22) is 0.22 μm.

5. The method for treating hydrogen sulfide in oil wells as described in claim 1, characterized in that, The preparation steps of the sulfate-reducing bacteria culture medium are as follows: Dissolve 0.5-1g of yeast extract, 0.3-0.5g of dipotassium hydrogen phosphate, 1.0-1.5g of ammonium chloride, 0.1-0.5g of anhydrous calcium chloride, 2.0-3.0g of magnesium sulfate heptahydrate, 0.5-1.0g of ferrous sulfate heptahydrate, 1.0-1.5g of sodium chloride, 0.3-0.5g of ascorbic acid, 0.3-0.5g of L-cyscysteine, 3-5g of anhydrous sodium sulfate, and 3.0-5.0g of sodium lactate in 1L of water, adjust the pH to 6.5-7.0, and obtain the sulfate-reducing bacteria culture medium after complete dissolution.

6. The method for treating hydrogen sulfide in oil wells as described in claim 1, characterized in that, The preparation steps of the culture medium for sulfate-reducing bacteria in the experimental oil reservoir cultured indoors are as follows: Dissolve 0.5-1g of yeast extract, 0.3-0.5g of dipotassium hydrogen phosphate, 1.0-1.5g of ammonium chloride, 0.1-0.5g of anhydrous calcium chloride, 2.0-3.0g of magnesium sulfate heptahydrate, 0.5-1.0g of ferrous sulfate heptahydrate, 1.0-1.5g of sodium chloride, 0.3-0.5g of ascorbic acid, 0.3-0.5g of L-cyscysteine, 3-5g of anhydrous sodium sulfate, and 3.0-5.0g of sodium lactate in 1L of produced fluid from an oil well in the test reservoir. After complete dissolution, remove the air from the anaerobic bottle using a vacuum pump, then purge with nitrogen for at least 4 cycles before sealing. Place the anaerobic bottle in a constant temperature incubator and incubate at the reservoir temperature for at least 7 days to obtain the culture medium for sulfate-reducing bacteria in the test reservoir culture.

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