Method for treating hydrogen sulfide in oil well

Abstract

The invention discloses a method for treating hydrogen sulfide in an oil well. The method comprises the following steps: (1) screening a test oil reservoir; (2) preparing an obligate strong SRB phage stock solution; (3) enriching the obligate strong SRB bacteriophage; (4) determining the optimal titer of the obligate strong SRB bacteriophage liquid; (5) selecting a bacteriophage fusion bactericide; (6) determining an optimal intervention point of bactericide use; and (7) field test and effect evaluation. The method has the following advantages: (1) the application range is wide, the method is simple and convenient, and the operability is good; (2) the pertinence is high; (3) the bacteriophage is used for sterilization, so that the drug resistance of bacteria can be prevented, and the service time of the bactericide can be prolonged; (4) the cost is reduced by more than 50% compared with the existing method; meanwhile, damage of toxicity of the bactericide to stratums is reduced, and economy and environmental protection are achieved.

Description

Technical Field

[0001] The present invention relates to the technical field of microbial control in oilfield systems. Specifically, the present invention discloses a method for treating hydrogen sulfide in oil wells. Background Art

[0002] Sulfate-reducing bacteria (abbreviated as SRB) is a general term for bacteria that can reduce SO 4 2- to H 2 S and obtain energy for themselves. SRB is a type of anaerobic microorganism that uses organic matter as a nutrient, and is widely present in oxygen-deficient environments such as soil, seawater, sludge, underground pipelines, and oil and gas wells with a pH value of 6-9. SRB is widely present in all aspects of the oilfield system. According to statistics, more than 70% of the H 2 S generated in domestic and foreign oilfield systems is caused by SRB, which can cause microbial corrosion, water quality deterioration, reduction of polymer viscosity, endanger human health, etc., seriously affecting the safe production of oilfields and causing environmental hazards and economic losses.

[0003] At present, the sterilization technologies for SRB mainly include physical methods, chemical methods and biological control methods. Physical methods often use cathodic protection, ultraviolet and ultrasonic sterilization, high-voltage pulse sterilization technology, etc. For example, Chinese invention patent application CN106542622 A discloses a magnetic field and ultrasonic treatment equipment for sulfate-reducing bacteria in oilfield produced fluid, which includes a metal pipe, a copper pipe, an ultrasonic generator, a transducer and a coil. The metal pipe is connected to the oilfield produced fluid delivery pipeline, the transducer is located outside the metal pipe, the transducer is closely connected to the outer diameter of the metal pipe, the ultrasonic generator is connected to the transducer, the copper pipe is located outside the metal pipe, the inner diameter of the copper pipe is closely connected to the outer diameter of the metal pipe, and the coil is wound outside the copper pipe. However, the physical method is difficult to operate and has high economic cost, and is not suitable for use on site in oil fields. Chemical method mainly refers to adding bactericide, is widely used in oil field, and the bactericide used in domestic oil field is mainly based on quaternary ammonium salt bactericide, such as Chinese invention patent application CN103168775A discloses a kind of double quaternary ammonium salt type gas field reinjection water bactericide and the bactericidal composition comprising the above-mentioned bactericide. Double quaternary ammonium salt of the present invention has higher positive charge density relative to traditional bactericide 1227, and the ability of adsorbing negatively charged bacterial cell surface increases, therefore has stronger bactericidal activity, and drug effect duration is long, foam is few. Double long-chain quaternary ammonium salt has one hydrophilic group and two lipophilic groups, has stronger ability to reduce surface tension, can enhance water solubility, even when water hardness is larger, also presents quite good solubility and stability. The above-mentioned gas field reinjection water bactericidal composition was used to conduct bacterial tests with reference to the extinction dilution method described in SY / T0532-93, and bactericidal experiments were conducted on sulfate-reducing bacteria (SRB), iron bacteria (FB) and saprophytic bacteria (TGB). The effective bactericidal concentration was 20-30ppm, and the bactericidal rate reached more than 99.9%, meeting the reinjection requirements. However, long-term use of bactericides will cause SRB to develop drug resistance, and the amount of agents used will increase accordingly. At the same time, chemical agents are highly toxic and will cause environmental pollution. How to improve the bactericidal efficiency of bactericides and reduce the amount of bactericides used is an urgent problem to be solved. The biological control method mainly uses the symbiotic, competitive, and antagonistic relationship between microorganisms to prevent and control harmful microorganisms. It is a green, environmentally friendly, economical and efficient sterilization method.

[0004] Chinese invention patent application CN101229943 A discloses a method for strengthening the activity of native microorganisms to control hydrogen sulfide. It uses the activation of nitrate-reducing bacteria in oilfield water to competitively inhibit the growth of SRB bacteria, thereby controlling hydrogen sulfide. However, this method is only applicable to water samples with nitrate-reducing bacteria, and biological competition can only suppress SRB bacteria to a certain level of quantity. When SRB bacteria develop resistance, there is a risk of rapid recovery of quantity, which increases the difficulty of later treatment.

[0005] At present, using bacteriophages to kill bacteria is a new research direction in biological control. Bacteriophages, also known as bacterial viruses, are a type of virus widely present in nature. Virulent bacteriophages can specifically invade "host" bacterial cells, replicate and proliferate within the host cells, produce progeny bacteriophages exponentially, and destroy the cell wall through enzymatic action, causing the bacteria to lyse and killing the bacteria through "lysis". Using bacteriophages to kill bacteria is a research idea for biological control of SRB and inhibition of H in oil wells 2 S, which has the advantages of high specificity, strong reproductive ability, and no drug resistance.

[0006] Chinese invention patent CN109439305 B discloses a method for improving the viscosity stability of polymer solutions, which specifically includes the isolation and screening of sulfate-reducing bacteria phages. By inhibiting SRB, the content of sulfide produced by its metabolism is reduced, thereby ensuring the polymer viscosity and effectively solving the problem of viscosity loss caused by sulfide produced by SRB during the transportation of oilfield polymer solutions.

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

[0008] Both of the above two patents involve the screening and isolation of SRB phages, but they fail to effectively evaluate and optimize the action effects of SRB phages, so the obtained SRB phages may not be in the optimal state and concentration; at the same time, through literature research, it is known that the bactericidal effect of using bacteriophages alone is about 90%, which can control the number of SRB at a low level, but cannot completely eliminate them; and currently, the highest bactericidal efficiency of bactericides used in oilfields against SRB is 90%. Using bactericides easily makes SRB develop drug resistance, and the bactericidal efficiency gradually decreases. The biological competition inhibition effect, the use of bacteriophages alone and the use of bactericides alone cannot achieve the effect of complete sterilization, and SRB will rapidly proliferate in the short term after use. Therefore, there is an urgent need for a method that can completely eliminate SRB bacteria in oil wells. Summary of the Invention

[0009] Object of the Invention: Aiming at sulfate-reducing bacteria, one of the sources of H produced in oil wells at present 2 S, the present invention provides a method for treating hydrogen sulfide in oil wells. On the one hand, the present invention provides a method for isolating and determining the optimal titer of a specific virulent bacteriophage against SRB. On the other hand, the specific virulent bacteriophage and bactericide are specifically fused to further enhance the bactericidal effect. The present invention can effectively control H in oil wells 2 S, greatly reduce the dosage of bactericides, reduce the damage to the formation, and at the same time reduce the cost 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 a stock solution of obligate virulent SRB phage;

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

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

[0015] (5) Selection of phage-fused bactericides;

[0016] (6) Determination of the best intervention point for using bactericides;

[0017] (7) Field tests and effect evaluations.

[0018] Further, the screening conditions for the test reservoirs in step (1) are as follows: H 2 S wellhead concentration > 10 ppm, and the concentration of sulfate-reducing bacteria present in the reservoir water sample > 25 cells / ml.

[0019] Furthermore, the sulfate-reducing bacteria are one or more of the genus Desulfovibrio, Desulfomonas, Desulfococcus, Desulfobacter, Desulfobullbus, Desulfobulbus, and Desulfotomaculum.

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

[0021] (21) Take at least 3 L of the produced water from the oil wells in the test reservoir. After standing indoors in a closed state for at least 36 h, the oil and water are separated. Take 1 L of the water sample from the lower layer and centrifuge it at 10000 - 12000 RPM for 15 - 30 minutes to remove the solid impurities therein, and collect the supernatant;

[0022] (22) Use a cellulose filter membrane to filter the supernatant. First, add 50 - 100 mL of autoclaved sulfate-reducing bacteria medium to an anaerobic bottle, then add 50 - 100 mL of the supernatant to it, and then inoculate 5 - 10 mL of the test oil reservoir sulfate-reducing bacteria culture solution cultured indoors and mix well. After using a vacuum pump to remove the air in the anaerobic bottle, introduce nitrogen or inert gas. After at least 4 cycles to achieve an anaerobic environment, seal it. After standing at room temperature for at least 30 minutes, place the anaerobic bottle in a constant temperature incubator and culture it at the oil reservoir temperature for at least 24 h; centrifuge at 10000 - 12000 RPM for 15 - 30 minutes and collect the supernatant. Then, the filtrate obtained by filtering the centrifuged supernatant through a cellulose filter membrane is the stock solution of obligate virulent SRB phage.

[0023] Furthermore, the pore diameter of the filtration holes of the cellulose filter membrane in step (22) is not greater than 0.22 μm, preferably 0.22 μm.

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

[0025] Furthermore, the preparation steps of the test oil reservoir sulfate-reducing bacteria culture solution cultured indoors are as follows:

[0026] Dissolve 0.5 - 1 g of yeast extract, 0.3 - 0.5 g of dipotassium hydrogen phosphate, 1.0 - 1.5 g of ammonium chloride, 0.1 - 0.5 g of anhydrous calcium chloride, 2.0 - 3.0 g of magnesium sulfate heptahydrate, 0.5 - 1.0 g of ferrous sulfate heptahydrate, 1.0 - 1.5 g of sodium chloride, 0.3 - 0.5 g of ascorbic acid, 0.3 - 0.5 g of L-cys cysteine, 3 - 5 g of anhydrous sodium sulfate, and 3.0 - 5.0 g of sodium lactate in 1 L of the produced fluid from the test oil reservoir oil well. After complete dissolution, use a vacuum pump to remove the air in the culture bottle, then introduce nitrogen for at least 4 cycles and seal it. Place the anaerobic bottle in a constant temperature incubator and culture it at the oil reservoir temperature for at least 7 d to obtain the test oil reservoir sulfate-reducing bacteria culture solution cultured indoors.

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

[0028] Take 10 - 20 mL of the original stock solution of the obligate virulent SRB phage and inoculate it into 1 - 2 L of the test reservoir sulfate - reducing bacteria culture solution in the logarithmic growth phase for enlarged culture. Cultivate it at the test reservoir temperature until the test reservoir sulfate - reducing bacteria culture solution becomes clear, then centrifuge and filter to collect the filtrate to obtain the obligate virulent SRB phage. After freeze - drying, obtain the dry powder of the obligate virulent SRB phage and store it at - 4°C;

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

[0030] Inoculate 0.1 - 0.3 wt% of the dry powder of the obligate virulent SRB phage into five portions of 1 L of the test reservoir sulfate - reducing bacteria culture solution in the logarithmic growth phase, and cultivate them at the reservoir temperature for 6 d, 8 d, 10 d, 12 d, and 15 d respectively. Then take 10 ml of the cultivated phage and add it to 1 L of the test reservoir sulfate - reducing bacteria culture solution in the logarithmic growth phase, and monitor the H 2 S concentration, and determine that the co - culture days of the phage and sulfate - reducing bacteria with the longest H 2 S inhibition time is the optimal titer of the obligate virulent SRB phage liquid.

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

[0032] Add five portions of 10 ml of the obligate virulent SRB phage with the optimal titer determined in step (4) to five portions of 1 L of the test reservoir sulfate - reducing bacteria culture solution in the logarithmic growth phase together with 10 ml of the bactericide THPS aqueous solution, 10 ml of the bactericide 1227 aqueous solution, 10 ml of the bactericide S - 29 aqueous solution, 10 ml of the bactericide KSG aqueous solution, and 10 ml of the bactericide SJT aqueous solution respectively. Cultivate them at the reservoir temperature and monitor the H 2 S concentration to determine the most suitable type of bactericide, where:

[0033] The concentrations of the bactericide THPS aqueous solution, 10 ml of the bactericide 1227 aqueous solution, 10 ml of the bactericide S - 29 aqueous solution, 10 ml of the bactericide KSG aqueous solution, and 10 ml of the bactericide SJT aqueous solution are all 50 mg / L.

[0034] Even further, after determining the type of bactericide, take 10 ml of the obligate virulent SRB phage with the optimal titer determined in step (4) and add it to 1 L of the test reservoir sulfate - reducing bacteria culture solution in the logarithmic growth phase together with 10 ml of bactericide aqueous solutions with different concentrations. Cultivate them at the reservoir temperature and monitor the H 2 S concentration to determine the most suitable bactericide concentration, where:

[0035] The setting range of the bactericide concentration is 10 mg / L - 50 mg / L.

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

[0037] Respectively add 10 portions of 10 ml of the obligate virulent SRB phage cultured to the optimal titer of the obligate virulent SRB phage liquid into 1 L of the test reservoir sulfate-reducing bacteria culture solution in the logarithmic growth phase. After co-culturing for 1 d, 2 d, 3 d, 4 d, 5 d, 6 d, 7 d, 8 d, 9 d, and 10 d respectively, add the optimal bactericide at the optimal concentration, culture at the reservoir temperature, and monitor the H 2 S concentration in the anaerobic bottle, where:

[0038] The number of days before adding the bactericide that can inhibit H 2 S to < 2 mg / L for the longest number of days is the optimal intervention point of the bactericide.

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

[0040] Add the obligate virulent SRB phage cultured to the optimal titer and the optimal type and concentration of the bactericide to the corresponding combined station of the test reservoir in the order of first the phage and then adding the bactericide at the optimal intervention point, each adding 0.2 - 0.5 PV. At the same time, monitor the H 2 S concentration at the wellhead of the corresponding oil well for effect evaluation.

[0041] Beneficial effects: A method for treating hydrogen sulfide in oil wells disclosed by the present invention uses a method of fusing an obligate virulent SRB phage with a bactericide to control H 2 S in oil wells, and has the following advantages compared with the prior art:

[0042] (1) It has a wide adaptation range. This invention is applicable to most oil wells with H 2 S problems. The method is simple and has good operability;

[0043] (2) It has strong pertinence. The present invention screens an obligate virulent SRB phage and determines the optimal titer of the phage to inhibit the growth of SRB in oil wells to achieve the purpose of inhibiting H 2 S, and can effectively regulate the harmful SRB flora in the reservoir to achieve long-term inhibition of H 2 S;

[0044] (3) Using phages to kill bacteria can prevent the generation of bacterial drug resistance and can extend the use time of the bactericide;

[0045] (4) Using phages to effectively fuse with bactericides to inhibit SRB can increase the bactericidal effect, while reducing the dosage of the bactericide by 70%, reducing the cost by more than 50% compared with the existing method; at the same time, reducing the harm of the toxicity of the bactericide to the formation, which is economical and environmentally friendly. Brief Description of the Drawings

[0046] Figure 1 It is a schematic diagram showing the effect of inhibiting hydrogen sulfide by co - culturing phages and SRB for different days in Example 1.

[0047] Figure 2 It is a schematic diagram showing the effect of inhibiting hydrogen sulfide by fusing phages with different types of fungicides in the examples.

[0048] Figure 3 It is a schematic diagram showing the effect of inhibiting hydrogen sulfide by different concentrations of THPS in Example 1.

[0049] Figure 4 It is a schematic diagram showing the effect of inhibiting hydrogen sulfide by co - culturing phages and SRB for different days in Example 2.

[0050] Figure 5 It is a schematic diagram showing the effect of inhibiting hydrogen sulfide by fusing phages with different types of fungicides in Example 2.

[0051] Figure 6 It is a schematic diagram showing the effect of inhibiting hydrogen sulfide by different concentrations of KSG in Example 2.

[0052] Figure 7 It is a schematic diagram showing the effect of inhibiting hydrogen sulfide by co - culturing phages and SRB for different days in Example 3.

[0053] Figure 8 It is a schematic diagram showing the effect of inhibiting hydrogen sulfide by fusing phages with different types of fungicides in Example 3.

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

[0055] Figure 10 It is a flow chart of a method for treating hydrogen sulfide in oil wells disclosed in the present invention. Detailed Description of the Embodiments

[0056] The following is a detailed description of the specific embodiments of the present invention.

[0057] Example 1

[0058] Well A in Test Block C of an oil production plant in Shengli Oilfield 13 with wellhead H 2 S concentration of 320 ppm, SRB quantity of 120 cells / ml, reservoir temperature of 52 °C, original H 2 The H2S treatment plan was to add bactericide 1227 periodically.

[0059] Using the method of the present invention to control H2S 2 S.

[0060] A method for treating hydrogen sulfide in oil wells, the specific steps are as follows:

[0061] (1) Screening of test reservoirs;

[0062] The H 2 S wellhead concentration of Well A > 10 ppm, and the concentration of sulfate-reducing bacteria in the reservoir water sample > 25 / ml, meeting the screening conditions of the test reservoir.

[0063] Among them: the sulfate-reducing bacteria are Desulfovibrio. In another embodiment, the sulfate-reducing bacteria are Desulfomonas. In another embodiment, the sulfate-reducing bacteria are Desulfococcus. In another embodiment, the sulfate-reducing bacteria are Desulfobacter. In another embodiment, the sulfate-reducing bacteria are Desulfobulbus. In another embodiment, the sulfate-reducing bacteria are Desulfobulbus. In another embodiment, the sulfate-reducing bacteria are Desulfotomaculum. In another embodiment, the sulfate-reducing bacteria include Desulfovibrio, Desulfomonas, Desulfococcus, Desulfobacter, Desulfobulbus, Desulfobulbus, Desulfotomaculum.

[0064] (2) Preparation of a stock solution of specific and virulent SRB phages;

[0065] (21) Take 4 L of the produced water from this oil well, let it stand indoors and sealed for 42 h, then the oil and water are separated. Take 1 L of the bottom water sample and centrifuge it at 11000 RPM for 20 minutes to remove the solid impurities therein, and collect the supernatant;

[0066] (22) Filter the supernatant with a 0.22 μm cellulose filter membrane, add 75 mL of autoclaved sulfate-reducing bacteria medium to an anaerobic bottle, then add 75 mL of the supernatant thereto, mix well after inoculating 7.5 mL of the test reservoir sulfate-reducing bacteria culture solution cultured indoors, evacuate the air in the anaerobic bottle with a vacuum pump and then pass nitrogen, seal it after 5 cycles to achieve an anaerobic environment, let it stand at room temperature for 40 minutes, then place the anaerobic bottle in a constant temperature incubator and culture it at 52 °C for 36 h; centrifuge at 11000 RPM for 20 minutes and collect the supernatant, and then filter the centrifuged supernatant through a 0.22 μm cellulose filter membrane. The obtained filtrate is the stock solution of obligate virulent SRB phage.

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

[0068] The specific steps for preparing the test reservoir sulfate-reducing bacteria culture solution cultured indoors are as follows: Dissolve 1 g of yeast extract, 0.5 g of dipotassium hydrogen phosphate, 1.5 g of ammonium chloride, 0.5 g of anhydrous calcium chloride, 2.5 g of magnesium sulfate heptahydrate, 1 g of ferrous sulfate heptahydrate, 1.5 g of sodium chloride, 0.3 g of ascorbic acid, 0.3 g of L-cys cysteine, 3.5 g of anhydrous sodium sulfate, and 5 g of sodium lactate in 1 L of produced oilfield fluid. After fully dissolving, evacuate the air in the culture bottle with a vacuum pump and then pass nitrogen for 5 cycles and seal it. Place the anaerobic bottle in a constant temperature incubator and culture it at 52 °C for 10 d to obtain it.

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

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

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

[0072] 0.2% of the above-mentioned obligate virulent SRB phage dry powder was inoculated into five portions of 1L test reservoir sulfate-reducing bacteria culture solutions in the logarithmic growth phase, and they were cultured at 52°C for 6d, 8d, 10d, 12d, and 15d respectively. Then, 10 ml of the cultured phage was taken and added to 1L of the test reservoir sulfate-reducing bacteria culture solution in the logarithmic growth phase, and the H 2 S concentration was monitored. The phage obtained after co-growing for 10d had the best inhibitory effect on H 2 S (see Figure 1 ), that is, the optimal titer of the phage liquid was 10d.

[0073] (5) Selection of phage fusion bactericides

[0074] Five portions of the phage (10 ml each) co-cultured with the test reservoir sulfate-reducing bacteria for 10d were separately added to 1L of the test reservoir sulfate-reducing bacteria culture solution in the logarithmic growth phase together with 10 ml of aqueous solutions of bactericides THPS, 1227, S-29, KSG, and SJT with a concentration of 50 mg / L, and they were cultured at 52°C, and the H 2 S concentration was monitored (see Figure 2 ). It was determined that the most suitable bactericide was bactericide THPS.

[0075] After determining the type, bactericides THPS with concentrations of 10, 20, 30, 40, and 50 mg / L were added to the test reservoir sulfate-reducing bacteria culture solution, and they were cultured and monitored according to the above method (the results are shown in Figure 3 ). It was determined that the optimal bactericide concentration was 40 mg / L.

[0076] (6) Determination of the best intervention point for bactericide use

[0077] 10 ml of the obligate virulent SRB phage cultured for 10d was added to 1L of the test reservoir sulfate-reducing bacteria culture solution in the logarithmic growth phase and co-cultured for 1d, 2d, 3d, 4d, 5d, 6d, 7d, 8d, 9d, and 10d respectively. Then, 40 mg / L of THPS was added, and they were cultured at 52°C, and the H 2 S concentration was monitored. Adding the bactericide 4 days after adding the phage could inhibit H 2 S at <2 mg / L for the longest number of days, that is, the best intervention point for the bactericide was 4 days after using the phage.

[0078] (7) Field test and effect evaluation

[0079] First, 0.4 PV of the obligate virulent SRB phage co-cultured for 10d was injected into the corresponding combined station of the test reservoir. 4 days later, 0.3 PV of the THPS bactericide with a concentration of 40 mg / L was added, and the H was monitored at the wellhead of the corresponding oil well2 The S concentration decreased from 320 ppm to 0 ppm in 5 days. The measure was effective, and the method of the present invention reduced the cost by 53.2% compared with the existing method.

[0080] Example 2

[0081] Test block Z of an oil production plant in Shengli Oilfield 2 In an oil well B, wellhead H 2 The S concentration was 150 ppm, the number of SRB was 50 per ml, the reservoir temperature was 63 °C, and no H 2 S treatment was carried out.

[0082] Using the method of the present invention to prevent and control H 2 S.

[0083] A method for treating hydrogen sulfide in oil wells, the specific steps are as follows:

[0084] (1) Screening of test reservoirs;

[0085] The H 2 S wellhead concentration of oil well A > 10 ppm, and the concentration of sulfate-reducing bacteria in the reservoir water sample > 25 per ml, meeting the screening conditions of the test reservoir.

[0086] Among them: the sulfate-reducing bacteria include the genus Desulfomonas.

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

[0088] (21) Take 5 L of the produced water from this oil well, let it stand in a closed environment indoors for 36 h, then the oil and water are separated. Take 1 L of the bottom water sample and centrifuge it at 10,000 RPM for 30 minutes to remove the solid impurities therein, and collect the supernatant;

[0089] (22) Filter the supernatant with a 0.22 μm cellulose filter membrane. First, add 50 mL of a sulfate-reducing bacteria medium sterilized by high pressure to an anaerobic bottle, then add 50 mL of the supernatant thereto, then inoculate 5 mL of a test reservoir sulfate-reducing bacteria culture solution cultured indoors and mix well. Use a vacuum pump to pump out the air in the anaerobic bottle and then introduce nitrogen. After 4 cycles to reach an anaerobic environment, seal it. Let it stand at room temperature for 30 minutes, then place the anaerobic bottle in a constant temperature incubator and culture it at 63 °C for 24 h; centrifuge it at 10,000 RPM for 30 minutes and then collect the supernatant. Then filter the centrifuged supernatant through a 0.22 μm cellulose filter membrane. The obtained filtrate is the stock solution of obligate virulent SRB phage, where:

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

[0091] The preparation steps of the test reservoir sulfate-reducing bacteria culture solution for indoor culture are as follows: Dissolve 0.5 g of yeast extract, 0.35 g of dipotassium hydrogen phosphate, 1.0 g of ammonium chloride, 0.1 g of anhydrous calcium chloride, 2.0 g of magnesium sulfate heptahydrate, 0.6 g of ferrous sulfate heptahydrate, 1.2 g of sodium chloride, 0.4 g of ascorbic acid, 0.4 g of L-cys cysteine, 3 g of anhydrous sodium sulfate, and 3.5 g of sodium lactate in 1 L of produced oil well fluid. After fully dissolving, evacuate the air in the culture bottle with a vacuum pump, then pass nitrogen for 4 cycles and seal it. Place the anaerobic bottle in a constant temperature incubator and culture it at 63 °C for 7 days to obtain the test reservoir sulfate-reducing bacteria culture solution for indoor culture.

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

[0093] Take 10 mL of the above-mentioned obligate virulent SRB phage stock solution and inoculate it into 1 L of the test reservoir sulfate-reducing bacteria culture solution in the logarithmic growth phase for enlarged culture. After culturing at 63 °C until the test reservoir sulfate-reducing bacteria culture solution 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 dry powder at -4 °C for standby.

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

[0095] Inoculate 0.1% of the above-mentioned obligate virulent SRB phage dry powder into five portions of 1 L of the test reservoir sulfate-reducing bacteria culture solution in the logarithmic growth phase, and culture them at 63 °C for 6 d, 8 d, 10 d, 12 d, and 15 d respectively. Take 10 ml of the cultured phage and add it to 1 L of the test reservoir sulfate-reducing bacteria culture solution in the logarithmic growth phase, and monitor the H 2 S concentration in the anaerobic bottle. The phage obtained by co-growing for 8 d has the best inhibitory effect on H 2 S (see Figure 4 ), that is, the optimal titer of the phage liquid is 8 d.

[0096] (5) Selection of phage fusion fungicides

[0097] Five portions of phages obtained by co-culturing with sulfate-reducing bacteria in the experimental reservoir for 8 days with each portion being 10 ml were respectively added to 1 L of the culture solution of sulfate-reducing bacteria in the experimental reservoir at the logarithmic growth stage, together with 10 ml of aqueous solutions of bactericides THPS, 1227, S-29, KSG, and SJT at a concentration of 50 mg / L. The mixture was cultured at 63°C, and the concentration of H 2 S in the anaerobic bottle was monitored (see Figure 5 ), and the most suitable bactericide was determined to be bactericide KSG.

[0098] After determining the type, 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 culture solution of sulfate-reducing bacteria in the experimental reservoir, and cultured and monitored according to the above method (see Figure 6 ), and the optimal bactericide concentration was determined to be 30 mg / L.

[0099] (6) Determination of the optimal intervention point for using the bactericide

[0100] Ten portions of 10 ml of obligate virulent SRB phages cultured for 8 days were respectively added to 1 L of the culture solution of sulfate-reducing bacteria in the experimental reservoir at the logarithmic growth stage. After co-culturing for 1 day, 2 days, 3 days, 4 days, 5 days, 6 days, 7 days, 8 days, 9 days, and 10 days respectively, 30 mg / L of bactericide KSG was added, and the mixture was cultured at 63°C, and the concentration of H 2 S in the anaerobic bottle was monitored. Adding the bactericide 8 days after adding the phage could inhibit H 2 S at <2 mg / L for the longest number of days, that is, the optimal intervention point for the bactericide was 8 days after using the phage.

[0101] (7) Field test and effect evaluation

[0102] First, 0.2 PV of obligate virulent SRB phages co-cultured for 8 days was injected into the corresponding combined station of the experimental reservoir. 8 days later, 0.4 PV of 30 mg / L of KSG bactericide was added, and the concentration of H 2 S was monitored at the wellhead of the corresponding oil well. The hydrogen sulfide was reduced from 150 ppm to 0 ppm in 4.5 days, and the measure was effective. Moreover, the method of the present invention reduced the cost by 50.7% compared with the existing method.

[0103] Example 3

[0104] Well C in the test block Y of a certain oil production plant in Shengli Oilfield 8 had a wellhead H 2 S concentration of 1200 ppm, an SRB count of 250 per ml, a reservoir temperature of 70°C, and the original H 2 S treatment plan was to add bactericide THPS periodically.

[0105] Control of H using the method of the present invention 2 S.

[0106] A method for treating hydrogen sulfide in oil wells, the specific steps are as follows:

[0107] (1) Screening of test reservoirs;

[0108] The H compliance of Oil Well A 2 The wellhead concentration of S > 10 ppm, and the concentration of sulfate-reducing bacteria in the reservoir water sample > 25 per ml, meeting the screening conditions of the test reservoir.

[0109] Among them: the sulfate-reducing bacteria include the genus Desulfomonas.

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

[0111] (21) Take 3 L of the produced water from this oil well, let it stand still in a closed environment indoors for 36 h, then the oil and water are separated. Take 1 L of the bottom water sample and centrifuge it at 12,000 RPM for 15 minutes to remove the solid impurities therein, and collect the supernatant;

[0112] (22) Filter the supernatant with a 0.22 μm cellulose filter membrane. First, add 100 mL of autoclaved sulfate-reducing bacteria medium to an anaerobic bottle, then add 00 mL of the supernatant thereto, and then inoculate 10 mL of the sulfate-reducing bacteria culture solution of the test reservoir cultured indoors and mix well. Use a vacuum pump to remove the air in the anaerobic bottle and then introduce nitrogen. After 6 cycles to achieve an anaerobic environment, seal it. Let it stand still at room temperature for 60 minutes, then place the anaerobic bottle in a constant temperature incubator and culture it at 70 °C for 48 h; centrifuge at 12,000 RPM for 15 minutes and collect the supernatant. Then filter the centrifuged supernatant through a 0.22 μm cellulose filter membrane. The obtained filtrate is the stock solution of obligate virulent SRB phage, where:

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

[0114] The preparation steps of the test oil reservoir sulfate-reducing bacteria culture solution cultured indoors are as follows: Add 0.7 g of yeast extract, 0.4 g of dipotassium hydrogen phosphate, 1.2 g of ammonium chloride, 0.4 g of anhydrous calcium chloride, 3 g of magnesium sulfate heptahydrate, 0.5 g of ferrous sulfate heptahydrate, 1.0 g of sodium chloride, 0.5 g of ascorbic acid, 0.5 g of L-cys cysteine, 5 g of anhydrous sodium sulfate, and 3.0 g of sodium lactate to 1 L of oil well produced fluid. After fully dissolving, evacuate the air in the culture flask with a vacuum pump, then pass nitrogen for 6 cycles and seal. Place the anaerobic flask in a constant temperature incubator and culture at 70 °C for 14 days to obtain the test oil reservoir sulfate-reducing bacteria culture solution cultured indoors.

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

[0116] Take 20 mL of the above-mentioned obligate virulent SRB phage stock solution and inoculate it into 2 L of the test oil reservoir sulfate-reducing bacteria culture solution in the logarithmic growth phase for enlarged culture. After culturing at 70 °C until the test oil reservoir sulfate-reducing bacteria culture solution 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 dry powder at -4 °C for standby.

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

[0118] Inoculate 0.3% of the above-mentioned obligate virulent SRB phage dry powder into five portions of 2 L of the test oil reservoir sulfate-reducing bacteria culture solution in the logarithmic growth phase, and culture them at 70 °C for 6 d, 8 d, 10 d, 12 d, and 15 d respectively. Take 10 mL of the cultured phage and add it to 1 L of the test oil reservoir sulfate-reducing bacteria culture solution in the logarithmic growth phase, and monitor the H 2 S concentration. The phage obtained by co-growing for 6 d has the best inhibitory effect on H 2 S (see Figure 7 ), that is, the optimal titer of the phage liquid is 6 d.

[0119] (5) Selection of phage fusion fungicides

[0120] Add five portions of 10 mL of the phage obtained by co-culturing with the test oil reservoir sulfate-reducing bacteria for 6 d, 10 mL of a 50 mg / L aqueous solution of the fungicide THPS, 10 mL of an aqueous solution of the fungicide 1227, 10 mL of an aqueous solution of the fungicide S-29, 10 mL of an aqueous solution of the fungicide KSG, and 10 mL of an aqueous solution of the fungicide SJT to 1 L of the test oil reservoir sulfate-reducing bacteria culture solution in the logarithmic growth phase at the same time, culture at 70 °C, and monitor the H 2 S concentration (see Figure 8 ), and determine that the most suitable fungicide is the fungicide SJT.

[0121] After determining the type, bactericides SJT with 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 solution of the experimental reservoir, and cultured and monitored according to the above method (see Figure 9 ), and the optimal bactericide concentration was determined to be 20 mg / L.

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

[0123] 10 ml of the obligate virulent SRB phage cultured for 6 days was separately added to 1 L of the sulfate-reducing bacteria culture solution of the experimental reservoir in the logarithmic growth phase. After co-culturing for 1 d, 2 d, 3 d, 4 d, 5 d, 6 d, 7 d, 8 d, 9 d, and 10 d respectively, 20 mg / L of bactericide SJT was added, cultured at 70 °C, and the H 2 S concentration was monitored. Adding the bactericide 10 days after adding the phage could inhibit H 2 S at <2 mg / L for the longest number of days, that is, the optimal intervention point of the bactericide was 10 days after using the phage.

[0124] (7) Field test and effect evaluation

[0125] First, 0.5 PV of the obligate virulent SRB phage co-cultured for 6 days was injected into the corresponding combined station of the experimental reservoir. 10 days later, 0.25 PV of 20 mg / L SJT bactericide was added, and the H 2 S concentration was monitored at the wellhead of the corresponding oil well. The hydrogen sulfide was reduced from 1200 ppm to 0 ppm in 3 days, and the measure was effective. Moreover, the method of the present invention reduced the cost by 58.3% compared with the existing method.

[0126] The above has made a detailed description of the implementation manner of the present invention. However, the present invention is not limited to the above implementation manner, and various changes can be made without departing from the gist of the present invention within the knowledge scope of those of ordinary skill in the art.

Claims

1. A method for controlling hydrogen sulfide in oil wells, characterized in that: The steps include: (1) Screening of test reservoirs; (2) Prepare a stock solution of specific and potent SRB phage; (3) Enrichment of obligate and potent SRB phages; (4) Determine the optimal titer of the obligate and potent SRB phage liquid; (5) Selection of bacteriophage fusion bactericides; (6) Determination of the optimal intervention point for fungicide use; (7) Field test and effect evaluation.

2. A method for controlling hydrogen sulfide in oil wells as claimed in claim 1, characterized in that: The screening conditions for the test reservoir in step (1) are as follows: H2S wellhead concentration>10ppm, and the concentration of sulfate-reducing bacteria in the reservoir water sample>25 / ml.

3. A method for controlling hydrogen sulfide in oil wells as claimed in claim 2, characterized in that: The sulfate-reducing bacteria are one or more of the genera Desulfovibrio, Desulfomonas, Desulfococcus, Desulfobacillus, Desulfolobus, Desulfobacterium, and Desulfoconchoides.

4. A method for controlling hydrogen sulfide in oil wells as claimed in claim 1, characterized in that: The specific steps of step (2) are as follows: (21) Take at least 3 L of produced water from the oil well in the test reservoir, let it stand in a closed room for at least 36 hours to separate the oil and water, take 1 L of the bottom water sample and centrifuge it at 10000-12000 RPM for 15-30 minutes to remove the solid impurities, and collect the supernatant; (22) Filter the supernatant using a cellulose filter membrane, add 50-100 mL of a sulfate-reducing bacteria culture medium sterilized by high pressure into an anaerobic bottle, then add 50-100 mL of the supernatant thereto, then inoculate 5-10 mL of a test oil reservoir sulfate-reducing bacteria culture medium cultured indoors and mix well, remove the air in the anaerobic bottle using a vacuum pump, then pass nitrogen or inert gas, perform at least 4 cycles to achieve an anaerobic environment and seal, let stand at room temperature for at least 30 minutes, place the anaerobic bottle in a constant temperature incubator, and culture at oil reservoir temperature for at least 24 hours; collect the supernatant after centrifugation at 10000-12000 RPM for 15-30 minutes, and then filter the supernatant after centrifugation through a cellulose filter membrane to obtain a filtrate that is the specific potent SRB phage stock solution.

5. A method for controlling hydrogen sulfide in oil wells as claimed in claim 4, characterized in that: The pore size of the filtration pores of the cellulose bacteria filter membrane in step (22) is not greater than 0.22 μm, preferably 0.22 μm.

6. A method for controlling hydrogen sulfide in oil wells as claimed in claim 4, characterized in that: The preparation steps of the sulfate-reducing bacteria culture medium are as follows: 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-cys cysteine, 3-5g of anhydrous sodium sulfate and 3.0-5.0g of sodium lactate are dissolved in 1L of water, the pH value is adjusted to 6.5-7.0, and the sulfate-reducing bacteria culture medium is obtained after it is fully dissolved.

7. A method for controlling hydrogen sulfide in oil wells as claimed in claim 4, characterized in that: The steps for preparing the experimental oil reservoir sulfate-reducing bacteria culture solution for indoor culture are as follows: 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-cys cysteine, 3-5g of anhydrous sodium sulfate and 3.0-5.0g of sodium lactate are dissolved in 1L of oil well produced fluid of the test reservoir. After being fully dissolved, the air in the culture bottle is evacuated by a vacuum pump, and nitrogen is passed through for at least 4 cycles and then sealed. The anaerobic bottle is placed in a constant temperature incubator and cultured at the reservoir temperature for at least 7 days to obtain the test reservoir sulfate-reducing bacteria culture solution cultured indoors.

8. A method for controlling hydrogen sulfide in oil wells as claimed in claim 1, characterized in that: The specific steps of step (3) are as follows: Take 10-20mL of the specific strong SRB phage stock solution and inoculate it into 1-2L of the test oil reservoir sulfate-reducing bacteria culture solution that has reached the logarithmic growth phase for expansion culture, culture it at the test oil reservoir temperature until the test oil reservoir sulfate-reducing bacteria culture solution becomes clear, collect the filtrate by centrifugation to obtain the specific strong SRB phage, and obtain the specific strong SRB phage dry powder after freeze-drying, which is stored at -4°C.

9. A method for controlling hydrogen sulfide in oil wells as claimed in claim 1, characterized in that: The specific steps of step (4) are as follows: 0.1-0.3wt% of the specific strong SRB phage dry powder is inoculated into five 1L culture solutions of sulfate-reducing bacteria in experimental oil reservoirs that have reached the logarithmic growth phase, and the cultures are cultured at the reservoir temperature for 6d, 8d, 10d, 12d, and 15d, respectively. 10ml of the cultured phage is added to 1L culture solution of sulfate-reducing bacteria in the experimental oil reservoirs that have reached the logarithmic growth phase, and the H2S concentration in the anaerobic bottle is monitored. The number of days of co-culture of the phage and sulfate-reducing bacteria that can inhibit H2S for the longest time is determined, which is the optimal titer of the specific strong SRB phage liquid.

10. A method for controlling hydrogen sulfide in oil wells as claimed in claim 9, characterized in that: The specific steps of step (5) are as follows: Add five portions of 10 ml of the optimal titer of the specific and potent SRB bacteriophage determined in step (4) and 10 ml of a fungicide THPS aqueous solution, 10 ml of a fungicide 1227 aqueous solution, 10 ml of a fungicide S-29 aqueous solution, 10 ml of a fungicide KSG aqueous solution, and 10 ml of a fungicide SJT aqueous solution to five portions of 1 L of a test reservoir sulfate-reducing bacteria culture solution that has reached the logarithmic growth phase, and culture at the reservoir temperature, and monitor the H2S concentration in the anaerobic bottle to determine the most suitable fungicide type, wherein: The concentrations of the fungicide THPS aqueous solution, 10 ml fungicide 1227 aqueous solution, 10 ml fungicide S-29 aqueous solution, 10 ml fungicide KSG aqueous solution, and 10 ml fungicide SJT aqueous solution are all 50 mg / L.

11. A method for controlling hydrogen sulfide in oil wells as claimed in claim 10, characterized in that: After determining the type of fungicide, take 10 ml of the optimal titer of the specific and virulent SRB bacteriophage determined in step (4) and 10 ml of different concentrations of fungicide aqueous solution and add them to 1 L of the test reservoir sulfate-reducing bacteria culture solution that has reached the logarithmic growth phase, culture at the reservoir temperature, and monitor the H2S concentration in the anaerobic bottle to determine the optimal fungicide concentration, where: The setting range of fungicide concentration is 10mg / L-50mg / L.

12. A method for controlling hydrogen sulfide in oil wells as claimed in claim 1, characterized in that: Step (6) includes the following steps: optimal titer of the specific potent SRB phage liquid Ten portions of 10 ml of the optimal titer of the specifically potent SRB phage liquid were added to 1L of the experimental reservoir sulfate-reducing bacteria culture solution that reached the logarithmic growth phase. After co-culturing for 1d, 2d, 3d, 4d, 5d, 6d, 7d, 8d, 9d, and 10d, the optimal fungicide at the optimal concentration was added, and the culture was carried out at the reservoir temperature. The H2S concentration in the anaerobic bottle was monitored, where: The longest number of days when phages were used before adding fungicides to suppress H2S to less than 2 mg / L was the best intervention point for fungicides.

13. A method for controlling hydrogen sulfide in oil wells as claimed in claim 1, characterized in that: Step (7) comprises the following steps: The specific and potent SRB phages cultured to the optimal titer and the fungicides of the optimal type and concentration were added to the joint station corresponding to the test reservoir in the order of phage first and then fungicides at the optimal insertion point, with 0.2-0.5PV of each added. At the same time, the H2S concentration was monitored at the wellhead of the corresponding oil well to evaluate the effect.

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