Combined system and method for killing sulfate reducing bacteria in oilfield produced water

Abstract

The invention provides a combined system and method for killing sulfate reducing bacteria in oilfield produced water. The combined system comprises an active oxygen solution sterilization unit, an oil removal tank, a coagulative precipitation tank, a filtering tank and a deoxidation tower, the active oxygen solution degerming unit comprises a partitioned excitation plasma reactor, a high-flux gas-liquid mixing and dissolving device, a decompression reactor and an oxygen tank; the partition excitation plasma reactor is used for ionizing and dissociating oxygen to generate oxygen active groups; the high-flux gas-liquid mixing and dissolving device is used for carrying out gas-liquid mixing and dissolving on water to be treated and oxygen active groups to generate an active oxygen solution; a water outlet of the high-flux gas-liquid mixing and dissolving device is connected to the reduced pressure reactor, water to be treated and an active oxygen solution fully react in the reduced pressure reactor, and sulfate reducing bacteria in the water to be treated are killed. The technical scheme provided by the invention solves the problems that the treatment effect of microorganisms in the oilfield produced water is undesirable, large-scale popularization cannot be realized, and the method is harmful to human bodies and the environment.

Description

Technical Field

[0001] The present invention relates to the technical field of oil sewage treatment, and in particular, to a combined system and method for killing sulfate-reducing bacteria in oilfield produced water. Background Art

[0002] At present, the water content in most of the oilfield produced fluids in China is 70-80%, and some even reach as high as 90%. With the increase of the production time, the water content in the produced fluid increases continuously. If a large amount of produced wastewater is directly discharged, it will cause environmental pollution problems and waste precious water resources at the same time. If the oily wastewater is treated and then reinjected into the formation to supplement the formation pressure, it can not only avoid environmental pollution, but also save a large amount of water resources. Therefore, treating the oily wastewater and then reinjecting it is an important way to realize the sustainable development of oilfields, improve the economic benefits of oilfields and save costs.

[0003] There are a large number of microorganisms in oilfield produced water, such as sulfate-reducing bacteria, saprophytic bacteria and iron bacteria, etc. During the growth and reproduction process of these microorganisms, they will cause serious corrosion of drilling and production equipment, injection pipelines and other metal fittings, block pipelines, damage oil layers, cause a decrease in injection volume, oil production and oil and gas quality, and also bring great difficulties to crude oil processing, resulting in great economic losses. Among them, the most harmful to the oilfield surface system is sulfate-reducing bacteria (SRB). SRB is an anaerobic bacterium commonly present in oilfield sewage, and the hydrogen sulfide produced by its metabolism will cause pipeline corrosion and endanger the life and health of operating personnel.

[0004] Currently, the commonly used methods for killing sulfate-reducing bacteria mainly include adding bactericides, ultraviolet method, membrane treatment process, biological competition inhibition method, etc.

[0005] Adding bactericides is currently the main method for oilfields to inhibit sulfate-reducing bacteria. Patents CN103663848A, CN104430564A, CN115804374A, CN114149062B, CN112342167B all use adding bactericides to treat oilfield produced water. However, the frequent and large-scale use of bactericides not only has high costs, but also promotes sulfate-reducing bacteria to produce drug resistance, and a large amount of bactericides are harmful to both the human body and the soil environment.

[0006] The ultraviolet sterilization method, also called the photocatalysis method, destroys the cell structure of bacteria through ultraviolet radiation, so that the bacteria lose the ability to replicate and reproduce. Its advantages are low cost, safe and environmentally friendly, and relatively simple operation. However, due to the weak penetration ability of ultraviolet rays, the suspended solids and oil in the sewage have a blocking and absorption effect on ultraviolet rays, which will reduce the light transmittance of water and thus affect the sterilization effect.

[0007] Membrane separation technology is a technology that uses the selective permeability of membranes for separation and purification. Patent CN103030193A uses a membrane treatment method to treat produced water. Ultrafiltration membranes and nanofiltration membranes can completely filter bacteria, and the quality of the treated water meets the requirements of reinjection water quality. However, the membrane treatment technology is costly and not suitable for the oilfield industry with large-scale water injection and drainage.

[0008] The biological competitive inhibition method is basically a nitrate-based microbial treatment technology. This method uses indigenous microorganisms in the oilfield, with low cost and no environmental pollution. However, the treatment effect of this method is closely related to the community structure of indigenous microorganisms in the oil reservoir, the physical and chemical properties of the oil reservoir, the dosage of activators, and the mutual relationship between communities. Since the microbial community structures in different oilfields are different, it is necessary to detect the microbial community structure in the oil reservoir, analyze the metabolic mechanism and mutual relationship of the microbial community during the inhibition process before using the biological competitive inhibition method, which greatly restricts the large-scale application of the biological inhibition method in different oilfields.

[0009] Therefore, developing a technical method for efficiently and rapidly treating harmful bacteria in produced water and controlling microbial pollution and corrosion in the oilfield water injection system has become an important and urgent task to ensure the sustainable development of China's oilfield industry. Summary of the Invention

[0010] In view of the above-mentioned technical problems that the treatment effect of microorganisms in oilfield produced water is not satisfactory, it cannot be widely promoted, and it is harmful to humans and the environment, a combined system and method for killing sulfate-reducing bacteria in oilfield produced water are provided.

[0011] The technical means adopted in the present invention are as follows:

[0012] A combined system for killing sulfate-reducing bacteria in oilfield produced water includes an active oxygen solution sterilization unit, an oil removal tank, a coagulation sedimentation tank, a filtration tank, and a deoxidation tower;

[0013] The active oxygen solution sterilization unit includes a partition excitation plasma reactor, a high-flux gas-liquid mixing device, a pressure reduction reactor, and an oxygen tank;

[0014] The water inlet of the oil removal tank is connected to the oilfield produced water through a first mechanical pump, the water outlet of the oil removal tank is connected to the coagulation sedimentation tank, and the water outlet of the coagulation sedimentation tank is connected to the water inlet of the filtration tank through a second mechanical pump;

[0015] The oxygen tank is used to provide oxygen for the partitioned excitation plasma reactor; the partitioned excitation plasma reactor is used to ionize and dissociate oxygen to generate oxygen active groups and introduce them into the high-flux gas-liquid mixing device; the high-flux gas-liquid mixing device consists of five Venturi ejectors connected in parallel; the water outlet of the filtration tank is connected to the water inlet of the high-flux gas-liquid mixing device through a third mechanical pump; the high-flux gas-liquid mixing device is used to perform gas-liquid mixing on the water to be treated and oxygen active groups to generate an active oxygen solution with ·OH, O3, and H2O2, and the total oxidant concentration in the active oxygen solution is 5-25 mg / L; the water outlet of the high-flux gas-liquid mixing device is connected to the pressure reduction reactor, and the water to be treated and the active oxygen solution fully react in the pressure reduction reactor to kill sulfate-reducing bacteria in the water to be treated; the water outlet of the pressure reduction reactor is connected to the deoxygenation tower; the water outlet of the deoxygenation tower is connected to the oilfield reinjection well.

[0016] Further, a water quality on-line detector is arranged between the third mechanical pump and the high-flux gas-liquid mixing device for on-line detection of water quality parameters of the water outlet of the filtration tank; a TRO concentration on-line detector is arranged between the high-flux gas-liquid mixing device and the pressure reduction reactor for on-line detection of the total oxidant concentration of the water outlet of the high-flux gas-liquid mixing device; a dissolved oxygen on-line detector is arranged between the deoxygenation tower and the oilfield reinjection well for on-line detection of the dissolved oxygen concentration of the water outlet of the deoxygenation tower.

[0017] Further, a first electromagnetic valve is arranged between the first mechanical pump and the oilfield produced water, and a first water flowmeter is arranged between the first mechanical pump and the water inlet of the oil removal tank; a second electromagnetic valve is arranged between the water outlet of the oil removal tank and the coagulation sedimentation tank; a third electromagnetic valve is arranged between the water outlet of the coagulation sedimentation tank and the second mechanical pump; a second water flowmeter is arranged between the water outlet of the filtration tank and the third mechanical pump; a fourth electromagnetic valve and a third water flowmeter are arranged in sequence between the water outlet of the pressure reduction reactor and the deoxygenation tower; a fifth electromagnetic valve is arranged between the deoxygenation tower and the oilfield reinjection well.

[0018] Further, branch pipelines are respectively arranged between the first mechanical pump and the oil removal tank, between the oil removal tank and the coagulation sedimentation tank, between the coagulation sedimentation tank and the second mechanical pump, between the filtration tank and the third mechanical pump, between the pressure reduction reactor and the deoxygenation tower, and between the deoxygenation tower and the oilfield injection well, and a first unit water intake valve, a second unit water intake valve, a third unit water intake valve, a fourth unit water intake valve, a fifth unit water intake valve, and a sixth unit water intake valve are respectively arranged on each branch pipeline.

[0019] Further, the oil removal tank is a vertical inclined plate oil removal tank; the residence time of the water to be treated in the oil removal tank is 1.5 - 2 h, the descending speed of the water to be treated is 1.0 - 1.6 mm / s, and the effective volume is 230 m 3 ; The water outlet of the oil removal tank is sampled by opening the water intake valve of the second unit, and the oil content of the water outlet of the oil removal tank is controlled within 50 mg / L, and the suspended solid content is controlled within 20 mg / L.

[0020] Further, the surface hydraulic load of the coagulation sedimentation tank is 3.0 - 6.0 m 3 / (m 2 ·h), the effective residence time of the sewage is 2 - 5 h, and the descending speed of the sewage is 0.5 - 1.7 mm / s; the water outlet of the coagulation sedimentation tank is sampled by opening the water intake valve of the third unit, and the suspended solid content of the water outlet of the coagulation sedimentation tank is controlled within 15 mg / L.

[0021] Further, the filtration speed of the filtration tank is 8 - 10 m / h, the suspended solid content of the water body is controlled within 5 mg / L, and the diameter of the suspended solid particles is within 4 μm.

[0022] Further, the total height of the filter layer in the filtration tank is 1.2 m, which is successively a fiber ball filter layer, a quartz sand filter layer, and a walnut shell filter layer from top to bottom. The walnut shell filter layer is used to remove oil and suspended solids in the water. The particle diameter of the quartz sand filter layer is 0.9 - 1.2 mm, and the fiber ball filter layer is made of modified fiber filaments tied together; the median diameter of the water quality particles of the walnut shell filter layer is less than 3 μm, the median diameter of the water quality particles of the quartz sand filter layer is less than 2 μm, and the median diameter of the water quality particles of the fiber ball filter layer is less than 1 - 2 μm.

[0023] Further, the oxygen flux of the partitioned excitation plasma reactor is 5 - 18 m 3 / h, the concentration of the generated oxygen active groups is controlled within 50 - 150 mg / L, and the output is 400 - 1000 g / h; the treatment time of the water to be treated in the active oxygen solution disinfection unit is 30 - 40 s, and the total oxidant concentration in the treated water is 0.5 - 1.2 mg / L; the maximum water flow rate of the high-flux gas-liquid mixing device exceeds 500 m 3 / h.

[0024] Further, the deoxygenation tower adopts vacuum deoxygenation technology, and the oxygen content of the water discharged from the deoxygenation tower is controlled within 0.05 mg / L.

[0025] The present invention also provides a method for killing sulfate-reducing bacteria in oilfield produced water, which uses the above-mentioned combined system for killing sulfate-reducing bacteria in oilfield produced water, and specifically includes the following steps:

[0026] (1) The water to be treated is pumped into the oil removal tank by the first mechanical pump for oil separation. The water to be treated after oil removal is discharged through the water outlet of the oil removal tank. Control the oil content in the water discharged from the oil removal tank within 50 mg / L and the suspended solid content within 20 mg / L.

[0027] (2) The water discharged from the oil removal tank is transported to the coagulation sedimentation tank for coagulation sedimentation. Control the suspended solid content in the water discharged from the coagulation sedimentation tank 7 within 15 mg / L.

[0028] (3) The water discharged from the coagulation sedimentation tank is transported to the filtration tank by the second mechanical pump for filtration. The filtration rate is 8 - 10 m / h. Control the water body suspended solid content at 5 mg / L and the suspended solid particle diameter within 4 μm.

[0029] (4) The water to be treated filtered by the filtration tank is pumped into the active oxygen solution disinfection unit by the third mechanical pump, and the water quality parameters of the water discharged from the filtration tank are detected online by the water quality online detector.

[0030] (5) O2 is provided for the partition - excited plasma reactor by the oxygen tank. The partition - excited plasma reactor uses O2 to prepare oxygen active groups. The process of the active oxygen solution disinfection unit using oxygen active groups to prepare the active oxygen solution is as follows: a) O2 is ionized and dissociated into oxygen active groups by the partition - excited plasma reactor; b) The water discharged from the filtration tank 8 is pumped into the Venturi ejector of the high - throughput gas - liquid mixing device by the third mechanical pump 103; c) The oxygen active groups generated by the partition - excited plasma reactor are also introduced into the Venturi ejector of the high - throughput gas - liquid mixing device, and are gas - liquid mixed with the water to be treated to produce the active oxygen solution.

[0031] During the preparation process of the active oxygen solution, the O2 flux of the partition - excited plasma reactor is 5 - 18 m 3 / h; the concentration of oxygen active groups is controlled at 50 - 150 mg / L, and the output is 400 - 1000 g / h; the power of the partition - excited plasma reactor is less than 20 kw.

[0032] Through the high - throughput gas - liquid mixing device, the oxygen active groups generate an active oxygen solution mainly composed of ·OH in water, which also includes O3 and H2O2. The gas - liquid mixing reaction time is 3 - 5 s, and the total oxidant concentration in the active oxygen solution is 5 - 25 mg / L.

[0033] (6) The total oxidant concentration of the effluent from the high-throughput gas-liquid mixing device is on-line detected by a TRO concentration on-line detector; the effluent from the high-throughput gas-liquid mixing device is introduced into a pressure reduction reactor, and the water to be treated and the reactive oxygen solution are fully contacted and reacted in the pressure reduction reactor. The reaction time is controlled within 10 - 20 s to kill the sulfate-reducing bacteria in the water to be treated and oxidatively degrade other organic pollutants. The total oxidant concentration in the water after the reaction is controlled within 0.5 - 1.2 mg / L;

[0034] (7) The effluent from the pressure reduction reactor is transported to a deoxygenation tower; a deoxidizer is added to the deoxygenation tower for further deoxygenation, and the oxygen content of the water discharged from the deoxygenation tower is controlled within 0.05 mg / L; the dissolved oxygen concentration of the effluent from the deoxygenation tower is on-line detected by a dissolved oxygen on-line detector;

[0035] (8) When the indexes of the treated oilfield produced water meet the requirements, the oilfield produced water is reinjected into the oil well.

[0036] Compared with the prior art, the present invention has the following advantages:

[0037] 1. The combined system for killing sulfate-reducing bacteria in oilfield produced water provided by the present invention has a single-unit treatment capacity of 1200 tons per day. The system adopts a treatment process of "oil removal - coagulation sedimentation - filtration - oxidative degradation of microorganisms by reactive oxygen solution - deoxygenation - oil well". The indexes of the reinjected water after treatment meet the standards of "Water Quality Index Method for Injection Water in Clastic Rock Reservoirs" (SYT 5329 - 2012).

[0038] 2. The combined system and method for killing sulfate-reducing bacteria in oilfield produced water provided by the present invention, the treatment time of the reactive oxygen solution sterilization unit is 30 - 40 s, the total oxidant concentration is prepared at 5 - 25 mg / L, the output is greater than 40 m 3 / h, it can realize automatic control operation, the total power of the whole machine is less than 20 kW, and the increased operation cost is only 1 - 2 cents per ton of water.

[0039] 3. The combined system and method for killing sulfate-reducing bacteria in oilfield produced water provided by the present invention, the high-throughput gas-liquid mixing device can realize the efficient gas-liquid mixing of oxygen active groups and the water to be treated, strengthening the efficacy of the reactive oxygen solution sterilization unit in treating microorganisms such as sulfate-reducing bacteria in oilfield produced water; the maximum water flow rate exceeds 500 m 3 / h, and the occupied space of the device is only 1 / 5 of the conventional mixing technology, and it can be transported by vehicle.

[0040] 4. The combined system and method for killing sulfate-reducing bacteria in produced water from oilfields provided by the present invention, wherein the active oxygen solution oxidatively degrades sulfate-reducing bacteria: The high-concentration active oxygen solution and the water to be treated fully react in a decompression reactor for 10 - 20 s. After the reaction, the concentration of the active oxygen solution is 0.5 - 1.2 mg / L, and sulfate-reducing bacteria are not detected in the treated produced water from oilfields.

[0041] 5. The combined system and method for killing sulfate-reducing bacteria in produced water from oilfields provided by the present invention, wherein the active oxygen solution oxidatively degrades microorganisms: Other microorganisms such as saprophytic bacteria and iron bacteria are not detected in the produced water from oilfields treated with the active oxygen solution, and there is no any strange smell or odor. The microbial content of the reinjected water all meets the national standard of "Water Quality Index Method for Water Injection in Clastic Rock Reservoirs" (SYT 5329 - 2012).

[0042] 6. The combined system and method for killing sulfate-reducing bacteria in produced water from oilfields provided by the present invention will not cause secondary pollution after oxidative treatment with the active oxygen solution.

[0043] For the above reasons, the present invention can be widely promoted in the field of petroleum sewage treatment. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the following drawings are some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0045] Figure 1 It is a schematic diagram of the combined system for killing sulfate-reducing bacteria in produced water from oilfields described in the present invention.

[0046] In the figure: 1. Partitioned excitation plasma reactor; 2. High-flux gas-liquid mixing device; 3. Decompression reactor; 4. Power distribution cabinet; 5. Oxygen tank; 6. Oil removal tank; 7. Coagulation sedimentation tank; 8. Filter tank; 9. Deoxidation tower; 101. First mechanical pump; 102. Second mechanical pump; 103. Third mechanical pump; 111. First water flowmeter; 112. Second water flowmeter; 113. Third water flowmeter; 121. First solenoid valve; 122. Second solenoid valve; 123. Third solenoid valve; 124. Fourth solenoid valve; 125. Fifth solenoid valve; 131. First unit water intake valve; 132. Second unit water intake valve; 133. Third unit water intake valve; 134. Fourth unit water intake valve; 135. Fifth unit water intake valve; 136. Sixth unit water intake valve; 141. On-line water quality detector; 142. On-line TRO concentration detector; 143. On-line dissolved oxygen detector. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0047] It should be noted that, without conflict, the embodiments in the present invention and the features in the embodiments may be combined with each other. The present invention will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0048] To make the objectives, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part rather than all of the embodiments of the present invention. The description of at least one exemplary embodiment below is actually only illustrative and in no way limits the present invention and its application or use. All other embodiments obtained by those of ordinary skill in the art based on the embodiments in the present invention without creative efforts shall fall within the scope of protection of the present invention.

[0049] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present invention. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "comprise" and / or "include" are used in this specification, they specify the presence of features, steps, operations, devices, components and / or their combinations.

[0050] Unless otherwise specifically stated, the relative arrangements of the components and steps, numerical expressions and values set forth in these embodiments do not limit the scope of the present invention. At the same time, it should be clear that, for the sake of description, the dimensions of the various parts shown in the drawings are not drawn in actual proportional relationship. Technologies, methods and devices known to those of ordinary skill in the relevant art may not be discussed in detail, but where appropriate, the said technologies, methods and devices should be regarded as part of the authorization specification. In all the examples shown and discussed herein, any specific values should be construed as merely exemplary and not as a limitation. Therefore, other examples of the exemplary embodiments may have different values. It should be noted that like reference numerals and letters denote like items in the following drawings, and thus, once an item is defined in one drawing, it does not need to be further discussed in subsequent drawings.

[0051] In the description of the present invention, it should be understood that the orientation or positional relationship indicated by orientation words such as "front, rear, upper, lower, left, right", "lateral, vertical, perpendicular, horizontal" and "top, bottom", etc. is usually based on the orientation or positional relationship shown in the drawings. It is only for the convenience of describing the present invention and simplifying the description. Without contrary instructions, these orientation words do not indicate and imply that the device or element referred to must have a specific orientation or be constructed and operated in a specific orientation. Therefore, it should not be construed as a limitation on the protection scope of the present invention: the orientation words "inside, outside" refer to the inside and outside relative to the contour of each component itself.

[0052] For the convenience of description, spatial relative terms such as "above...", "over...", "on the upper surface of...", "above" etc. can be used here to describe the spatial positional relationship between a device or feature shown in the drawings and other devices or features. It should be understood that the spatial relative terms are intended to include different orientations in use or operation in addition to the orientation described in the drawings for the device. For example, if the device in the drawings is inverted, the device described as "above other devices or structures" or "over other devices or structures" will then be positioned as "below other devices or structures" or "under other devices or structures". Thus, the exemplary term "above..." can include both the orientations of "above..." and "below...". The device can also be positioned in other different ways (rotated 90 degrees or in other orientations), and corresponding interpretations should be made for the spatial relative descriptions used here.

[0053] In addition, it should be noted that using words such as "first", "second", etc. to limit components is only for the convenience of distinguishing the corresponding components. Without additional statements, the above words have no special meanings. Therefore, it should not be construed as a limitation on the protection scope of the present invention.

[0054] Example 1

[0055] As Figure 1 shown, the present invention provides a combined system for killing sulfate-reducing bacteria in produced water from oilfields. The active oxygen solution is used to treat sulfate-reducing bacteria in the produced water from oilfields, combining the surface treatment process of reinjected water in oilfields and the oxidation treatment process of the active oxygen solution. It includes an active oxygen solution bacteria removal unit A, an oil removal tank 6, a coagulation sedimentation tank 7, a filtration tank 8 and a deoxidation tower 9;

[0056] The active oxygen solution bacteria removal unit A includes a partition excitation plasma reactor 1, a high-throughput gas-liquid mixing device 2, a pressure reduction reactor 3 and an oxygen tank 5;

[0057] The water inlet of the oil removal tank 6 is connected to the produced water from the oilfield through the first mechanical pump 101. The water outlet of the oil removal tank 6 is connected to the coagulation sedimentation tank 7. The water outlet of the coagulation sedimentation tank 7 is connected to the water inlet of the filtration tank 8 through the second mechanical pump 102. The oil removal tank 6, the coagulation sedimentation tank 7, and the filtration tank 8 are respectively used for removing oil, coagulating and sedimenting, and filtering the water to be treated.

[0058] The reactive oxygen solution disinfection unit A is used to generate a reactive oxygen solution to kill sulfate-reducing bacteria in the produced water from the oilfield.

[0059] The oxygen tank 5 is used to provide oxygen for the partition-excited plasma reactor 1. The partition-excited plasma reactor 1 is used to ionize and dissociate oxygen to generate oxygen active groups, which are introduced into the high-flux gas-liquid mixing device 2. The high-flux gas-liquid mixing device 2 is composed of five Venturi ejectors connected in parallel. The water outlet of the filtration tank 8 is connected to the water inlet of the high-flux gas-liquid mixing device 2 through the third mechanical pump 103. The high-flux gas-liquid mixing device 2 is used to mix the water to be treated introduced from the filtration tank 8 and the oxygen active groups introduced from the partition-excited plasma reactor 1 to generate a reactive oxygen solution with ·OH, O3, and H2O2, and the total oxidant concentration in the reactive oxygen solution is 5-25 mg / L. The water outlet of the high-flux gas-liquid mixing device 2 is connected to the pressure reduction reactor 3. The water to be treated and the reactive oxygen solution fully react in the pressure reduction reactor 3 to kill sulfate-reducing bacteria in the water to be treated and oxidize and degrade other organic pollutants. The water outlet of the pressure reduction reactor 3 is connected to the deoxygenation tower 9. The deoxygenation tower 9 is used to deoxygenate the water to be treated. The water outlet of the deoxygenation tower 9 is connected to the oilfield reinjection well to reinject the produced water from the oilfield.

[0060] Further, a water quality on-line detector 141 is arranged between the third mechanical pump 103 and the high-flux gas-liquid mixing device 2, which is used for on-line detecting water quality parameters such as turbidity and pH of the water discharged from the filtration tank 8. A TRO concentration on-line detector 142 is arranged between the high-flux gas-liquid mixing device 2 and the pressure reduction reactor 3, which is used for on-line detecting the total oxidant concentration of the water discharged from the high-flux gas-liquid mixing device 2 (reactive oxygen solution). A dissolved oxygen on-line detector 143 is arranged between the deoxygenation tower 9 and the oilfield reinjection well, which is used for on-line detecting the dissolved oxygen concentration of the water discharged from the deoxygenation tower 9.

[0061] Further, a first solenoid valve 121 is provided between the first mechanical pump 101 and the produced water from the oilfield, and a first water flowmeter 111 is provided between the first mechanical pump 101 and the water inlet of the oil removal tank 6; a second solenoid valve 122 is provided between the water outlet of the oil removal tank 6 and the coagulation sedimentation tank 7; a third solenoid valve 123 is provided between the water outlet of the coagulation sedimentation tank 7 and the second mechanical pump 102; a second water flowmeter 112 is provided between the water outlet of the filtration tank 8 and the third mechanical pump 103; a fourth solenoid valve 124 and a third water flowmeter 113 are successively provided between the water outlet of the decompression reactor 3 and the deoxidation tower 9; a fifth solenoid valve 125 is provided between the deoxidation tower 9 and the oilfield reinjection well; each water flowmeter is used to monitor the water flow rate in the pipeline.

[0062] Further, branch pipelines are respectively provided between the first mechanical pump 101 and the oil removal tank 6, between the oil removal tank 6 and the coagulation sedimentation tank 7, between the coagulation sedimentation tank 7 and the second mechanical pump 102, between the filtration tank 8 and the third mechanical pump 103, between the decompression reactor 3 and the deoxidation tower 9, and between the deoxidation tower 9 and the oilfield injection well. First unit water intake valves 131, second unit water intake valves 132, third unit water intake valves 133, fourth unit water intake valves 134, fifth unit water intake valves 135 and sixth unit water intake valves 136 are respectively provided on each of the branch pipelines.

[0063] Further, the oil removal tank 6 adopts a vertical inclined plate oil removal tank, the inclined plate spacing is 80 - 100 mm, the inclined plate inclination angle is 45 - 60°, the horizontal projection load of the inclined plate is 1.5×10 -4 ~2.0×10 -4 m 3 / (s·m 2 ), the inclined plate specifications are: plate length 1360 mm, plate width 760 mm, plate thickness 1.6 - 1.9 mm, each inclined plate has 5 - 8 waves, the wavelength is about 120 mm, and the wave height is 15 - 25 mm; the residence time of the water to be treated in the oil removal tank 6 is 1.5 - 2 h, the descending speed of the water to be treated is 1.0 - 1.6 mm / s, and the effective volume is 230 m 3 ; By opening the second unit water intake valve 132 to take water for detection of the water outlet of the oil removal tank 6, the oil content of the water outlet of the oil removal tank 6 is controlled within 50 mg / L, and the suspended solid content is within 20 mg / L.

[0064] Further, the surface hydraulic load of the coagulation sedimentation tank 7 is 3.0 - 6.0 m 3 / (m 2·h), the effective residence time of the sewage is 2 - 5 h, and the sewage descending speed is 0.5 - 1.7 mm / s; the water outlet of the coagulation sedimentation tank 7 is detected by opening the third unit water intake valve 133, and the suspended solid content of the water outlet of the coagulation sedimentation tank 7 is controlled within 15 mg / L.

[0065] Further, the filtration speed of the filtration tank 8 is 8 - 10 m / h, the water outlet of the filtration tank 8 is detected by opening the fourth unit water intake valve 134, and the suspended solid content of the water body is controlled at 5 mg / L, and the diameter of the suspended solid particles is within 4 μm.

[0066] Further, the total height of the filter layer in the filtration tank 8 is 1.2 m, which is successively a fiber ball filter layer, a quartz sand filter layer and a walnut shell filter layer from top to bottom. The walnut shell filter layer is used to remove oil and suspended solids in the water. The particle diameter of the quartz sand filter layer is 0.9 - 1.2 mm, and the fiber ball filter layer is made of high-quality imported modified fiber filaments tied together; the median diameter of the water quality particles of the walnut shell filter layer is less than 3 μm, the median diameter of the water quality particles of the quartz sand filter layer is less than 2 μm, and the median diameter of the water quality particles of the fiber ball filter layer is less than 1 - 2 μm.

[0067] Further, the oxygen flux of the zoned excitation plasma reactor 1 is 5 - 18 m 3 / h, the concentration of the generated oxygen active groups is controlled at 50 - 150 mg / L, and the output is 400 - 1000 g / h; the treatment time of the water to be treated in the active oxygen solution sterilization unit A is 30 - 40 s, and the total oxidant concentration in the treated water is 0.5 - 1.2 mg / L; the maximum water passing flow rate of the high-flux gas-liquid mixing device 2 exceeds 500 m 3 / h.

[0068] Further, the zoned excitation plasma reactor 1 includes a high-power inverter, 24 zoned excitation units and a cooling water circulation device. The zoned excitation unit is composed of a small high-frequency transformer and an atmospheric pressure non-equilibrium plasma reactor.

[0069] Further, the zoned excitation plasma reactor 1 is provided with a power distribution cabinet 4 for power supply.

[0070] Further, the deoxidation tower 9 adopts vacuum deoxidation technology, the oxygen content of the water discharged from the deoxidation tower 9 is controlled within 0.05 mg / L, and the oxygen content of the water discharged from the deoxidation tower 9 is generally 0.3 - 3.0 mg / L. Therefore, a deoxidizer (Na2SO3) is added for further deoxidation.

[0071] The present invention also provides a method for killing sulfate-reducing bacteria in produced water from oilfields, which adopts the above-mentioned combined system for killing sulfate-reducing bacteria in produced water from oilfields, and specifically includes the following steps:

[0072] (1) Open the first solenoid valve 121 and the first unit water intake valve 131 to take water for detecting the produced water from the oilfield. Pump the water to be treated into the oil removal tank 6 through the first mechanical pump 101 for separation and oil removal. The oil removal tank 6 is a vertical inclined plate oil removal tank. The water to be treated is preliminarily separated by gravity in the upper separation area of the oil removal tank 6, and larger oil droplet particles are separated. The water to be treated is further separated through the inclined plate area, and the separated oil droplet particles float to the water surface. The water to be treated after oil removal is discharged through the water outlet of the oil removal tank 6. The residence time of the water to be treated in the oil removal tank 6 is 1.5 - 2 h, the descending speed of the water to be treated is 1.0 - 1.6 mm / s, and the effective volume is 230 m 3 ; Take water through the second unit water intake valve 132 to detect the water outlet of the oil removal tank 6, and control the oil content in the water outlet of the oil removal tank 6 within 50 mg / L and the suspended solid content within 20 mg / L;

[0073] (2) Open the second solenoid valve 122, and the water outlet of the oil removal tank 6 is transported to the coagulation sedimentation tank 7 for coagulation sedimentation. The surface hydraulic load of the coagulation sedimentation tank 7 is 3.0 - 6.0 m 3 / (m 2 ·h), the effective residence time of the sewage is 2 - 5 h, the descending speed of the sewage is 0.5 - 1.7 mm / s. Take water through the third unit water intake valve 133 to detect the water outlet of the coagulation sedimentation tank 7, and control the suspended solid content in the water outlet of the coagulation sedimentation tank 7 within 15 mg / L;

[0074] (3) Open the third solenoid valve 123, and transport the water outlet of the coagulation sedimentation tank 7 to the filtration tank 8 for filtration through the second mechanical pump 102. The filtration speed is 8 - 10 m / h. Take water through the fourth unit water intake valve 134 to detect the water outlet of the filtration tank 8, and control the suspended solid content in the water body within 5 mg / L and the diameter of the suspended solid particles within 4 μm;

[0075] (4) Monitor the water flow through the second water flowmeter 112, pump the water to be treated filtered by the filtration tank 8 into the active oxygen solution sterilization unit A through the third mechanical pump 103, and perform on-line detection of water quality parameters such as turbidity and pH of the water outlet of the filtration tank 8 through the water quality on-line detector 141, and the concentration of the active oxygen solution in the active oxygen solution sterilization unit A can be determined according to the water quality condition;

[0076] (5) Provide O2 to the zone-excited plasma reactor 1 through the oxygen tank 5 and supply power through the power distribution cabinet 4. The zone-excited plasma reactor 1 uses O2 to prepare oxygen active groups. The process of the active oxygen solution sterilization unit A preparing the active oxygen solution using the oxygen active groups is as follows: a) O2 is ionized and dissociated into oxygen active groups by the zone-excited plasma reactor 1; b) The water pumped out of the filtration tank 8 is pumped into the Venturi injector of the high-flux gas-liquid mixing device 2 through the third mechanical pump 103; c) The oxygen active groups generated by the zone-excited plasma reactor 1 are also introduced into the Venturi injector of the high-flux gas-liquid mixing device 2, and are gas-liquid mixed with the water to be treated to produce a high-concentration active oxygen solution;

[0077] During the preparation process of the active oxygen solution, the O2 flux of the zone-excited plasma reactor 1 is 5 - 18 m 3 / h; the concentration of oxygen active groups is controlled at 50 - 150 mg / L, and the output is 400 - 1000 g / h; the power of the zone-excited plasma reactor 1 is less than 20 kw;

[0078] Through the high-flux gas-liquid mixing device 2, the oxygen active groups generate an active oxygen solution mainly composed of ·OH in water, and also include active groups such as O3 and H2O2. The gas-liquid mixing reaction time is 3 - 5 s, and the total oxidant concentration in the active oxygen solution is 5 - 25 mg / L;

[0079] (6) Online detect the total oxidant concentration of the water discharged from the high-flux gas-liquid mixing device 2 (active oxygen solution) through the TRO concentration online detector 142. The water discharged from the high-flux gas-liquid mixing device 2 is introduced into the decompression reactor 3. The water to be treated and the active oxygen solution are fully contacted and reacted in the decompression reactor 3. The reaction time is controlled at 10 - 20 s to kill microorganisms such as sulfate-reducing bacteria in the water to be treated and oxidize and degrade other organic pollutants. The total oxidant concentration in the water after the reaction is controlled at 0.5 - 1.2 mg / L;

[0080] (7) Open the fourth solenoid valve 124, and the water discharged from the decompression reactor 3 is transported to the deoxygenation tower 9; The deoxygenation tower 9 is added with a deoxidizer (Na2SO3) for further deoxygenation. The dissolved oxygen content of the water discharged from the deoxygenation tower 9 is controlled within 0.05 mg / L; The dissolved oxygen content in the water discharged from the deoxygenation tower 9 is generally 0.3 - 3.0 mg / L, so a deoxidizer (Na2SO3) is added for further deoxygenation; Online detect the dissolved oxygen concentration of the water discharged from the deoxygenation tower 9 through the dissolved oxygen online detector 143;

[0081] (8) Take water from the deoxidization tower 9 for detection by opening the water intake valve 136 of the sixth unit to ensure that sulfate-reducing bacteria are not detected in the treated water. After the treated oilfield produced water meets the requirements of the water quality standard in the "Water Quality Index Method for Injection Water in Clastic Rock Reservoirs" SYT 5329-2012, open the fifth solenoid valve 125 to reinject the oilfield produced water into the oil well.

[0082] The combined system and method for killing sulfate-reducing bacteria in oilfield produced water described in the present invention adopt a treatment process of "oil removal - coagulation sedimentation - filtration - oxidation and degradation of microorganisms by active oxygen solution - deoxidization - oil well", and the treatment capacity can reach 1200 tons per day; the partition-excited plasma reactor adopts the atmospheric pressure ionization discharge method, and the total oxidant concentration of the prepared active oxygen solution can reach 5-25 mg / L, the output is greater than 40 m 3 / h, and the total power of the whole machine is less than 20 kW; the high-flux gas-liquid mixing device has a maximum water flow rate exceeding 500 m 3 / h; through the hydrodynamic cavitation effect, the oxygen active groups are fully gas-liquid mixed with the filtered water to generate a high-concentration active oxygen solution, realizing the oxidation and degradation of sulfate-reducing bacteria and organic pollutants; the treatment time of the active oxygen solution sterilization unit is 30-40 s, the concentration of the active oxygen solution after the reaction is 0.5-1.2 mg / L, and sulfate-reducing bacteria, saprophytic bacteria, iron bacteria and other microorganisms are not detected in the treated water; the treated water has no peculiar smell or odor, the suspended solid concentration is less than 5 mg / L, the oil content is within 10 mg / L, the dissolved oxygen content is within 0.05 mg / L, and there is no biological toxicity. All water quality indicators can meet the national standard of "Water Quality Index Method for Injection Water in Clastic Rock Reservoirs" (SYT 5329-2012).

[0083] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements for some or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A combined system for killing sulfate-reducing bacteria in produced water from oilfields, characterized in that, It includes an active oxygen solution sterilization unit, an oil removal tank, a coagulation sedimentation tank, a filtration tank and a deoxidation tower; The active oxygen solution sterilization unit includes a partition excitation plasma reactor, a high-throughput gas-liquid mixing device, a decompression reactor and an oxygen tank; The water inlet of the oil removal tank is connected to the oilfield produced water through a first mechanical pump, the water outlet of the oil removal tank is connected to the coagulation sedimentation tank, and the water outlet of the coagulation sedimentation tank is connected to the water inlet of the filtration tank through a second mechanical pump; The oxygen tank is used to provide oxygen for the partition excitation plasma reactor; the partition excitation plasma reactor is used to ionize and dissociate oxygen to generate oxygen active groups and introduce them into the high-throughput gas-liquid mixing device; the high-throughput gas-liquid mixing device is composed of five Venturi injectors in parallel; the water outlet of the filtration tank is connected to the water inlet of the high-throughput gas-liquid mixing device through a third mechanical pump; the high-throughput gas-liquid mixing device is used to perform gas-liquid mixing on the water to be treated and oxygen active groups to generate an active oxygen solution with ·OH, O3, and H2O2, and the total oxidant concentration in the active oxygen solution is 5-25 mg / L; the water outlet of the high-throughput gas-liquid mixing device is connected to the decompression reactor, and the water to be treated and the active oxygen solution fully react in the decompression reactor to kill sulfate-reducing bacteria in the water to be treated; The water outlet of the decompression reactor is connected to the deoxidation tower; the water outlet of the deoxidation tower is connected to the oilfield reinjection well.

2. The combined system for killing sulfate-reducing bacteria in produced water from oilfields according to claim 1, wherein, A water quality on-line detector is arranged between the third mechanical pump and the high-throughput gas-liquid mixing device for on-line detection of water quality parameters of the effluent of the filtration tank; a TRO concentration on-line detector is arranged between the high-throughput gas-liquid mixing device and the decompression reactor for on-line detection of the total oxidant concentration of the effluent of the high-throughput gas-liquid mixing device; a dissolved oxygen on-line detector is arranged between the deoxidation tower and the oilfield reinjection well for on-line detection of the dissolved oxygen concentration of the effluent of the deoxidation tower.

3. The combined system for killing sulfate-reducing bacteria in produced water from oilfields according to claim 1, characterized in that, A first solenoid valve is arranged between the first mechanical pump and the oilfield produced water, and a first water flowmeter is arranged between the first mechanical pump and the water inlet of the oil removal tank; a second solenoid valve is arranged between the water outlet of the oil removal tank and the coagulation sedimentation tank; a third solenoid valve is arranged between the water outlet of the coagulation sedimentation tank and the second mechanical pump; a second water flowmeter is arranged between the water outlet of the filtration tank and the third mechanical pump; a fourth solenoid valve and a third water flowmeter are arranged in sequence between the water outlet of the decompression reactor and the deoxidation tower; a fifth solenoid valve is arranged between the deoxidation tower and the oilfield reinjection well.

4. The combined system for killing sulfate-reducing bacteria in produced water from oil fields according to claim 1, wherein Branch pipelines are respectively arranged between the first mechanical pump and the oil removal tank, between the oil removal tank and the coagulation sedimentation tank, between the coagulation sedimentation tank and the second mechanical pump, between the filtration tank and the third mechanical pump, between the decompression reactor and the deoxidation tower, and between the deoxidation tower and the oilfield injection well, and a first unit water intake valve, a second unit water intake valve, a third unit water intake valve, a fourth unit water intake valve, a fifth unit water intake valve and a sixth unit water intake valve are respectively arranged on each branch pipeline.

5. The combined system for killing sulfate-reducing bacteria in produced water from oilfields according to claim 4, wherein, The oil removal tank used is a vertical inclined plate oil removal tank; the residence time of the water to be treated in the oil removal tank is 1.5 - 2 h, the descending speed of the water to be treated is 1.0 - 1.6 mm / s, and the effective volume is 230 m 3 ; The water outlet of the oil removal tank is sampled and tested by opening the water intake valve of the second unit, and the oil content of the water outlet of the oil removal tank is controlled within 50 mg / L, and the suspended solid content is within 20 mg / L.

6. The combined system for killing sulfate-reducing bacteria in produced water from oil fields according to claim 4, wherein, The surface hydraulic load of the coagulation sedimentation tank is 3.0 - 6.0 m 3 / (m 2 ·h), the effective residence time of the sewage is 2 - 5 h, and the sewage descending speed is 0.5 - 1.7 mm / s; the water outlet of the coagulation sedimentation tank is detected by taking water through opening the third unit water intake valve, and the suspended solid content in the water outlet of the coagulation sedimentation tank is controlled within 15 mg / L.

7. The combined system for killing sulfate-reducing bacteria in produced water from oil fields according to claim 1, wherein The filtration rate of the filtration tank is 8 - 10 m / h, controlling the suspended solid content in the water body at 5 mg / L and the suspended matter particle diameter within 4 μm.

8. The combined system for killing sulfate-reducing bacteria in produced water from oil fields according to claim 1, wherein The total height of the filter layer in the filtration tank is 1.2 m. From top to bottom, it is successively a fiber ball filter layer, a quartz sand filter layer, and a walnut shell filter layer. The walnut shell filter layer is used to remove oil and suspended matter in the water. The particle diameter of the quartz sand filter layer is 0.9 - 1.2 mm. The fiber ball filter layer is formed by tying modified fiber filaments; the median particle diameter of the effluent quality of the walnut shell filter layer is less than 3 μm, the median particle diameter of the effluent quality of the quartz sand filter layer is less than 2 μm, and the median particle diameter of the effluent quality of the fiber ball filter layer is less than 1 - 2 μm; the deoxidation tower adopts vacuum deoxidation technology, and the dissolved oxygen content of the water discharged from the deoxidation tower is controlled within 0.05 mg / L.

9. The combined system for killing sulfate-reducing bacteria in produced water from oilfields according to claim 1, wherein The oxygen flux of the described partitioned excitation plasma reactor is 5 to 18 m 3 / h, the concentration of oxygen active groups generated is controlled at 50 to 150 mg / L, and the output is 400 to 1000 g / h; the treatment time of the water to be treated in the active oxygen solution sterilization unit is 30 to 40 s, and the total oxidant concentration in the treated water is 0.5 to 1.2 mg / L; the maximum water flow rate of the high-flux gas-liquid mixing device exceeds 500 m 3 / h.

10. A method for killing sulfate-reducing bacteria in produced water from oilfields, characterized in that, The combined system for killing sulfate-reducing bacteria in oilfield produced water as described in Claim 2 is adopted, specifically including the following steps: (1) Pump the water to be treated into the oil removal tank through the first mechanical pump for oil separation. The water to be treated after oil removal is discharged through the outlet of the oil removal tank; control the oil content in the effluent of the oil removal tank within 50 mg / L and the suspended solid content within 20 mg / L. (2) The effluent of the oil removal tank is transported to the coagulation sedimentation tank for coagulation sedimentation, controlling the suspended matter content in the effluent of the coagulation sedimentation tank within 15 mg / L. (3) Pump the effluent of the coagulation sedimentation tank into the filtration tank through the second mechanical pump for filtration. The filtration rate is 8 - 10 m / h, controlling the suspended solid content in the water body at 5 mg / L and the suspended matter particle diameter within 4 μm. (4) Pump the water to be treated filtered by the filtration tank into the active oxygen solution sterilization unit through the third mechanical pump, and conduct on-line detection of the water quality parameters of the effluent of the filtration tank through the on-line water quality detector. (5) Provide O2 for the partition-excited plasma reactor through the oxygen tank. The partition-excited plasma reactor uses O2 to prepare oxygen active groups. The process of the active oxygen solution sterilization unit using oxygen active groups to prepare the active oxygen solution is as follows: a) O2 is ionized and dissociated into oxygen active groups by the partition-excited plasma reactor; b) Pump the effluent of the filtration tank 8 into the Venturi injector of the high-flux gas-liquid mixing device through the third mechanical pump 103; c) The oxygen active groups generated by the partition-excited plasma reactor are also introduced into the Venturi injector of the high-flux gas-liquid mixing device to conduct gas-liquid mixing with the water to be treated, generating the active oxygen solution. During the preparation of the reactive oxygen solution, the O2 flux of the zoned excitation plasma reactor is 5 to 18 m 3 / h; the concentration of oxygen active groups is controlled at 50 to 150 mg / L, and the output is 400 to 1000 g / h; the power of the zoned excitation plasma reactor is less than 20 kw; Through the high-flux gas-liquid mixing device, oxygen active groups generate an active oxygen solution mainly composed of ·OH in water, and also include O3 and H2O2. The gas-liquid mixing reaction time is 3 - 5 s, and the total oxidant concentration in the active oxygen solution is 5 - 25 mg / L. (6) The total oxidant concentration of the effluent from the high-throughput gas-liquid mixing device is on-line detected by a TRO concentration on-line detector; the effluent from the high-throughput gas-liquid mixing device is fed into a pressure-reducing reactor, and the water to be treated and the reactive oxygen solution are fully contacted and reacted in the pressure-reducing reactor. The reaction time is controlled within 10 - 20 s to kill the sulfate-reducing bacteria in the water to be treated and oxidize and degrade other organic pollutants. The total oxidant concentration in the water after the reaction is controlled within 0.5 - 1.2 mg / L; (7) The effluent from the pressure-reducing reactor is transported to a deoxidation tower; a deoxidant is added to the deoxidation tower for further deoxidation, and the oxygen content of the water discharged from the deoxidation tower is controlled within 0.05 mg / L; the dissolved oxygen concentration of the effluent from the deoxidation tower is on-line detected by a dissolved oxygen on-line detector; (8) When the indexes of the treated oilfield produced water meet the requirements, the oilfield produced water is reinjected into the oil well.

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