A modular produced water treatment system for oil fields and a control method

Abstract

An oilfield produced water modular treatment system and control method, comprising a primary sedimentation module, a premixing module, a gas floatation treatment module, a depth filtration module and a fine filtration module connected in series through pipelines, the outlets of the depth filtration module and the fine filtration module being connected with a water storage tank module through pipelines, the dosing ports of the premixing module, the gas floatation treatment module and the fine filtration module being connected with a dosing module through pipelines, and valves being installed on the pipelines connecting the modules; the depth filtration module comprises a first-stage high-efficiency rotating bed filtration device and a second-stage high-efficiency rotating bed filtration device, and the first-stage high-efficiency rotating bed filtration device and the second-stage high-efficiency rotating bed filtration device are connected through pipelines and valves and can be switched between parallel connection, series connection and separate opening; the present application can increase or decrease the number of filtration modules or realize series-parallel connection of the first-stage and second-stage high-efficiency rotating bed filtration devices according to different qualities of produced water to meet the requirements of different types of water treatment, and solve the problem of fixed process of traditional methods.

Description

Technical Field

[0001] This invention relates to the field of oilfield produced water treatment technology, and in particular to a modular oilfield produced water treatment system and control method. Background Technology

[0002] In oilfield development, produced water treatment is a crucial step. With onshore and offshore oilfields generally entering the tertiary recovery stage, the large-scale application of enhanced oil recovery technologies such as polymer flooding and binary / ternary composite flooding has led to a year-on-year increase in produced water volume, characterized by "high levels of pollution, high concentrations of wastewater, and high environmental degradation." Direct discharge of this wastewater without effective treatment not only causes severe environmental pollution but also results in a significant waste of water resources. Treating and reinjecting it into the formation not only solves the wastewater discharge problem but also replenishes formation energy, representing the mainstream direction for the resource utilization of oilfield wastewater.

[0003] Currently, most oilfield produced water treatment processes are fixed combinations, such as the traditional "sedimentation-flotation-filtration" process, which has the following technical defects: First, it has poor adaptability, unable to flexibly adjust the process configuration according to fluctuations in influent water quality (such as changes in suspended solids content and oil content) and effluent indicator requirements (such as different formation reinjection standards), resulting in unstable treatment effects and difficulty in meeting different reinjection or discharge standards; Second, it has limited treatment efficiency, with traditional processes being ineffective in removing fine suspended solids and emulsified oil, easily leading to clogging of subsequent filtration units and affecting the stable operation of the system; Third, it requires large amounts of chemicals, with traditional processes requiring the addition of large amounts of demulsifiers, flocculants, and bactericides, which not only increases treatment costs but also generates a large amount of chemical sludge, making subsequent sludge disposal difficult; Fourth, the filtration system lacks flexibility, with existing multi-stage filtration units mostly having a fixed series structure, unable to switch operating modes according to water quality conditions, resulting in low filtration effect and system fault tolerance. Although ceramic membrane filtration units can improve effluent accuracy, the membrane surface is prone to adsorbing oil, and the effects of traditional clean water backwashing or chemical backwashing are limited, easily causing membrane fouling and shortening membrane lifespan. Summary of the Invention

[0004] The first objective of this invention is to provide a modular treatment system for oilfield produced water. This system employs a modular design, allowing for optimized configuration of the number of modules and operating modes based on different water quality and treatment standards. It effectively treats suspended solids and mineral oil, and utilizes ozone-enhanced premixed demulsification, ozone-enhanced air flotation, and ozone-enhanced ceramic membrane backwashing for multi-stage, high-efficiency ozone utilization, effectively reducing reagent dosage. Through the synergistic effect of the first and second-stage high-efficiency rotary bed filtration devices and the ceramic membrane filtration device, it ensures that the effluent meets reinjection requirements, achieving efficient, flexible, and environmentally friendly oilfield produced water treatment. It features high treatment efficiency, simple process, and adaptability. The invention offers several advantages, including adaptability to various operating conditions. A second objective of this invention is to provide a modular control method for oilfield produced water. This method achieves flexible combination and adjustment of treatment steps through modular process reconstruction. It combines multi-stage efficient utilization of ozone with targeted reagent dosage. Through synergistic treatment steps such as primary sedimentation separation, ozone-enhanced premixing, ozone-enhanced flotation, multi-stage vortex deep filtration, and ceramic membrane fine filtration, it selectively removes suspended solids, emulsified oil, and other pollutants from the produced water according to its specific quality. Simultaneously, it achieves resource utilization of floating oil and compliant effluent. This method boasts advantages such as flexible operating condition adaptation, high treatment efficiency, low reagent dosage, and stable operation.

[0005] To achieve the first objective mentioned above, this invention provides a modular treatment system for oilfield produced water, comprising a primary sedimentation module, a premixing module, an air flotation module, a deep filtration module, and a fine filtration module connected in series via pipelines. The outlets of the deep filtration module and the fine filtration module are connected to a storage tank module via pipelines. The dosing ports of the premixing module, the air flotation module, and the fine filtration module are respectively connected to a dosing module via pipelines. Valves are installed on the pipelines connecting each module. The primary sedimentation module includes at least one stage of sedimentation device. The premixing module includes a mixer and an ozone generator, which is connected to the mixer, the air flotation module, and the fine filtration module via pipelines. The air flotation module includes an air flotation device, an oil recovery device, and a sludge treatment device. The deep filtration module includes a first-stage high-efficiency rotary bed filter and a second-stage high-efficiency rotary bed filter, which are connected via pipelines and valves and can be switched between parallel, series, and individual operation. The fine filtration module includes a ceramic membrane filter, which includes a filter tank and a ceramic flat sheet membrane system installed within the filter tank.

[0006] In this embodiment, the sedimentation device includes a produced water outlet, an oil outlet, and a sedimentation sludge outlet. A sedimentation sludge discharge valve is installed on the sedimentation sludge outlet. The oil outlet is connected to the oil inlet of the oil recovery device of the air flotation treatment module through a pipeline. The outlet of the sedimentation sludge discharge valve is connected to the inlet of the sludge discharge pump through a pipeline. The outlet of the sludge discharge pump is connected to the inlet of the sludge treatment device of the air flotation treatment module through a pipeline.

[0007] In this embodiment, the mixer is provided with a first inlet, a second inlet and a third inlet. The first inlet of the mixer is connected to the outlet of the sedimentation device through a pipe, the second inlet is connected to the outlet of the ozone generator through a pipe, and the third inlet is connected to the outlet of the dosing module through a pipe. The outlet of the mixer is connected to the inlet of the flotation device through a pipe. A premixing inlet valve is installed on the first inlet of the mixer. The inlet of the premixing inlet valve is connected to the outlet pipe of the mixer through a first through pipe. An air flotation inlet valve is installed on the first through pipe.

[0008] In this embodiment, the ozone generator is provided with a first outlet, a second outlet, a third outlet, and a fourth outlet. The first outlet of the ozone generator is connected to the inlet of the mixer via a pipe, and a premixed ozone aeration valve is installed on this pipe. The second outlet of the ozone generator is connected to the aeration plate at the bottom of the flotation device via a pipe, and a flotation ozone aeration valve is installed on this pipe. The third outlet of the ozone generator is connected to the aeration duct in the ceramic flat sheet membrane module of the fine filtration module via a pipe, and a membrane ozone aeration valve is installed on this pipe. The fourth outlet of the ozone generator is connected to the backwash pipe of the fine filtration module via a pipe, and a membrane ozone backwash aeration valve is installed on this pipe.

[0009] In this embodiment, the top of the air flotation device is equipped with an oil and sludge scraper. The outlet of the oil and sludge scraper is connected to the inlet of the oil recovery device through a pipe. The bottom of the air flotation device is equipped with a sludge discharge port, which is connected to the inlet of the sludge treatment device through a pipe. An air flotation sludge discharge valve is installed on this pipe. The outlet of the air flotation device is connected to a three-way pipe. The first outlet of the three-way pipe is connected to the inlet of the first filter water inlet pump, and the second outlet of the three-way pipe is connected to the inlet of the second filter water inlet pump. A first-stage high-efficiency vortex filter inlet valve is installed on the inlet of the first-stage high-efficiency vortex filter. The inlet of the first-stage high-efficiency vortex filter inlet valve is connected to the outlet of the first filter water inlet pump and the second through pipe through pipes respectively. An air flotation outlet valve is installed on the second through pipe, which is connected to the inlet of the water storage tank module through a pipe. The outlet of the second filter water inlet pump is connected to the inlet of the second-stage high-efficiency vortex filter through a fifth through pipe, which is also equipped with a second-stage high-efficiency vortex filter inlet valve.

[0010] In this embodiment, a third through pipe is installed at the outlet of the first-stage high-efficiency vortex filter, which is connected to a fourth through pipe. A parallel outlet valve for the first-stage high-efficiency vortex filter is installed on the third through pipe. The inlet of the parallel outlet valve for the first-stage high-efficiency vortex filter is connected to the inlet of the second-stage high-efficiency vortex filter via a pipe. A series outlet valve for the high-efficiency vortex filter is installed on this pipe. A third pipe is installed at the outlet of the second-stage high-efficiency vortex filter, which is connected to a fourth through pipe. An outlet valve for the second-stage high-efficiency vortex filter is installed on the third pipe. An outlet valve for the vortex filter is installed on the fourth through pipe. The outlet of the outlet valve for the vortex filter is connected to the second through pipe. The inlet of the outlet valve for the vortex filter is connected to the inlet of the filter tank in the fine filtration module via the fourth through pipe. A membrane tank inlet valve is installed on the fourth through pipe.

[0011] In this embodiment, the outlet of the first-stage high-efficiency vortex filter is connected to the outlet of the water storage tank module via a first pipe. The first pipe is equipped with a backwash inlet valve and a first backwash inlet pump for the first-stage high-efficiency vortex filter. The outlet of the second-stage high-efficiency vortex filter is connected to the outlet of the water storage tank module via a second pipe. The second pipe is equipped with a backwash inlet valve and a second backwash inlet pump for the second-stage high-efficiency vortex filter. The inlet of the backwash inlet valve of the first-stage high-efficiency vortex filter is connected to the outlet of the backwash inlet valve of the second-stage high-efficiency vortex filter via a fifth pipe. Next, a high-efficiency vortex filter device with a series backwash valve is installed on the fifth pipeline; the first-stage high-efficiency vortex filter device and the second-stage high-efficiency vortex filter device are respectively equipped with backwash outlets. The backwash outlet of the first-stage high-efficiency vortex filter device is equipped with a first-stage high-efficiency vortex filter device backwash outlet valve, and the backwash outlet of the second-stage high-efficiency vortex filter device is equipped with a second-stage high-efficiency vortex filter device backwash outlet valve. The backwash outlet valves of the first-stage high-efficiency vortex filter device and the second-stage high-efficiency vortex filter device are connected to the return water port of the air flotation device through pipelines.

[0012] In this embodiment, the filter tank is provided with an oil discharge port, which is connected to an oil recovery device through a pipeline. The oil discharge device is used to discharge the floating oil intercepted by the ceramic membrane filtration into the oil recovery device. The bottom of the filter tank is provided with a sludge discharge port, which is connected to the sludge discharge pump of the sludge treatment device through a pipeline. A membrane tank sludge discharge valve is installed on this pipeline.

[0013] In this embodiment, the dosing module includes a pretreatment agent dosing device, a PAC dosing device, a PAM dosing device, a membrane acid washing dosing device, and a membrane alkali washing dosing device. The pretreatment agent dosing device is connected to the third inlet of the mixer in the premixing module via a pipeline. The PAC dosing device and the PAM dosing device are connected to the flotation device dosing port in the flotation treatment module via pipelines. The membrane alkali washing dosing device and the membrane acid washing dosing device are connected to the ceramic flat sheet membrane system of the fine filtration module via pipelines.

[0014] To achieve the second objective mentioned above, this invention provides a modular control method for oilfield produced water, used to control the opening and closing of valves and pumps in the aforementioned modular oilfield produced water treatment system, thereby enabling pipeline reconfiguration. The method specifically includes the following steps:

[0015] S1. Detect the oil content and suspended solids content of the extracted water, and adjust the opening and closing of valves and pumps accordingly;

[0016] Scenario 1: When oil content > 1000 mg / L and suspended solids content > 500 mg / L:

[0017] The opening and closing of valves and pumps are controlled to achieve the first form of pipeline reconstruction, so that the primary sedimentation module, premixing module, air flotation treatment module, deep filtration module, and fine filtration module are connected in series; the dosing system is activated, and the pretreatment agent dosing device adds demulsifier;

[0018] Scenario 2: When oil content < 200 mg / L and suspended solids content < 200 mg / L:

[0019] The second form of pipeline reconfiguration is achieved by controlling the opening and closing of valves and pumps, so that the primary sedimentation module, air flotation treatment module, and deep filtration module are connected in series, and the first-stage high-efficiency rotary bed filter and the second-stage high-efficiency rotary bed filter in the deep filtration module are operated in parallel; the pretreatment agent dosing device, membrane acid washing dosing device, and membrane alkali washing dosing device are not activated, while the PAC dosing device and PAM dosing device are activated.

[0020] Scenario 3: When the oil concentration is 200–1000 mg / L and the suspended solids content is 200–500 mg / L:

[0021] The opening and closing of valves and pumps are controlled to achieve the third form of pipeline reconfiguration, forming a primary sedimentation module, a premixing module, an air flotation treatment module, and a deep filtration module connected in series. The first-stage high-efficiency rotary bed filter and the second-stage high-efficiency rotary bed filter in the deep filtration module are connected in parallel. The pretreatment agent dosing device, PAC dosing device, and PAM dosing device are turned on, while the membrane acid washing dosing device and the membrane alkali washing dosing device are turned off.

[0022] S2. Detect the sulfur and iron ion content in the extracted water;

[0023] When the sulfide ion concentration is >25 mg / L or the iron ion concentration is >20 mg / L, sodium hypochlorite is added to the pretreatment agent dosing device.

[0024] Due to the above structure, the present invention has the following advantages:

[0025] 1. This device, through its modular design, achieves multi-stage synergistic treatment via primary sedimentation, premixing, flotation, deep filtration, and fine filtration modules. This results in significant removal of fine suspended solids and emulsified oil, with the effluent consistently meeting the reinjection requirements of different oilfield formations, thus avoiding clogging issues in subsequent filtration stages. Furthermore, by controlling the opening and closing of valves and pumps, modules can be flexibly added or removed, and treatment steps switched, based on influent water quality and effluent standards. This allows for process reconfiguration, adapting to different types of produced water treatment needs, such as high emulsification and high oil content, low oil content and low suspended solids, and high sulfur and high iron ion concentrations, thus solving the problem of fixed processes in traditional methods.

[0026] 2. The ozone generator is connected to multiple modules through pipelines, thereby applying ozone to enhanced premixing treatment, enhanced air flotation separation, and ceramic membrane fine filtration. Utilizing the oxidation, demulsification, and sterilization effects of ozone, it enhances processes such as pre-oxidation, air flotation, and membrane backwashing, significantly reducing the dosage of demulsifiers, bactericides, coagulants, coagulant aids, and membrane backwashing agents. This reduces the amount of chemical sludge generated, lowers reagent costs and sludge disposal pressure, while simultaneously improving filtration time and the lifespan of the ceramic membrane.

[0027] 3. The dosing module includes a pretreatment agent dosing device, a PAC dosing device, a PAM dosing device, a membrane acid washing dosing device, and a membrane alkali washing dosing device. The type of pretreatment agent can be selected according to the water quality characteristics of the oilfield produced water, and the agents are added as needed at each stage. This solves the problem of fixed agent dosing in traditional methods, realizes precise agent dosing, and further reduces treatment costs.

[0028] 4. This device realizes multi-stage rotary bed filtration series / parallel switching for deep filtration, adjusts filtration accuracy and treatment capacity according to water quality, and is equipped with an overpass pipe to ensure system operation, facilitates inspection and maintenance, and has a unified oil recovery and sludge treatment procedure, which centrally recovers floating oil in each stage, and the qualified effluent is directly reinjected into the formation. Attached Figure Description

[0029] Figure 1 This is a process flow diagram of the present invention.

[0030] Figure 2 For the present invention Figure 1 Enlarged view of point A in the middle.

[0031] Figure 3 For the present invention Figure 1 Enlarged view of point B in the middle.

[0032] Figure 4 This is a schematic diagram of the present invention.

[0033] In the attached diagram: 1. Primary sedimentation module; 2. Sedimentation device; 3. Premixing module; 4. Ozone generator; 5. Mixer; 6. Air flotation module; 7. Sludge treatment device; 8. Air flotation device; 9. Oil recovery device; 10. Deep filtration module; 11. First-stage high-efficiency rotary bed filter; 12. Second-stage high-efficiency rotary bed filter; 13. Fine filtration module; 14. Blower; 15. Ceramic flat sheet membrane module; 16. Filter tank; 17. Permeate system; 18. Backwashing system; 19. Storage tank module; 20. Chemical dosing. Modules; 21. Pretreatment agent dosing device; 22. PAC dosing device; 23. PAM dosing device; 24. Membrane acid washing dosing device; 25. Membrane alkaline washing dosing device; 101. First crossing pipe; 102. Second crossing pipe; 103. Third crossing pipe; 104. Fourth crossing pipe; 105. Fifth crossing pipe; 201. Sludge pump; 202. First filter feed water pump; 203. Second filter feed water pump; 204. First backwash feed water pump; 205. Second backwash feed water pump; 206. Membrane permeate pump; 207. 111. Membrane backwash pump; 112. Sedimentation device sludge discharge valve; 113. Premixed water inlet valve; 114. Air flotation water inlet valve; 115. Premixed ozone aeration valve; 116. Air flotation ozone aeration valve; 117. Air flotation sludge discharge valve; 118. Membrane ozone backwash aeration valve; 119. Air flotation outlet valve; 120. First-stage high-efficiency vortex filter inlet valve; 121. First-stage high-efficiency vortex filter backwash outlet valve; 122. Second-stage high-efficiency vortex filter backwash outlet valve; 123. Vortex filter outlet valve; 124. Membrane tank inlet. Valves; 124. Series outlet valve of high-efficiency rotary bed filter; 125. Inlet valve of second-stage high-efficiency rotary bed filter; 126. Parallel outlet valve of first-stage high-efficiency rotary bed filter; 127. Outlet valve of second-stage high-efficiency rotary bed filter; 128. Sludge discharge valve of membrane tank; 129. Backwash inlet valve of first-stage high-efficiency rotary bed filter; 130. Backwash inlet valve of second-stage high-efficiency rotary bed filter; 131. Series backwash valve of high-efficiency rotary bed filter; 132. Membrane permeate valve; 133. Membrane backwash valve; 134. Membrane ozone aeration valve. Detailed Implementation

[0034] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0035] Furthermore, the technical solutions of the various embodiments of the present invention can be combined with each other, but only if they are feasible for those skilled in the art. If the combination of technical solutions is contradictory or cannot be implemented, it should be considered that such combination of technical solutions does not exist and is not within the scope of protection claimed by the present invention.

[0036] like Figures 1 to 4 As shown, a modular treatment system for oilfield produced water includes a primary sedimentation module 1, a premixing module 3, an air flotation treatment module 6, a deep filtration module 10, and a fine filtration module 13 connected in sequence by pipelines. The dosing ports of the premixing module 3, the air flotation treatment module 6, and the fine filtration module 13 are respectively connected to the dosing module 20 by pipelines.

[0037] The primary sedimentation module 1 includes at least one sedimentation device 2; the premixing module 3 includes a mixer 5 and an ozone generator 4, and is used to premix and demulsify the produced water; the flotation treatment module 6 includes a flotation device 8, an oil recovery device 9, and a sludge treatment device 7; the deep filtration module 10 includes a first-stage high-efficiency rotary bed filter 11 and a second-stage high-efficiency rotary bed filter 12, with a bypass pipe between the first and second-stage high-efficiency rotary bed filters; the fine filtration module 13 includes a ceramic membrane filter, which includes a filter tank 16 and a ceramic flat sheet membrane system installed in the filter tank 16, and the ceramic flat sheet membrane system includes a ceramic flat sheet membrane module 15, a product water system 17, an aeration device, and an ozone-enhanced backwashing system 18.

[0038] The settling device 2 includes a produced water outlet, an oil outlet, and a settling sludge outlet. A settling device sludge discharge valve 111 is installed on the settling sludge outlet. The oil outlet is connected to the oil inlet of the oil recovery device 9 of the air flotation treatment module 6 through a pipeline. The outlet of the settling device sludge discharge valve 111 is connected to the inlet of the sludge discharge pump 201 through a pipeline. The outlet of the sludge discharge pump 201 is connected to the inlet of the sludge treatment device 7 of the air flotation treatment module 6 through a pipeline.

[0039] In this embodiment, the mixer 5 is a static mixer. The mixer 5 has a first inlet, a second inlet, and a third inlet. The first inlet of the mixer 5 is connected to the produced water outlet of the sedimentation device 2 via a pipe, the second inlet is connected to the outlet of the ozone generator 4 via a pipe, and the third inlet is connected to the outlet of the dosing module 20 via a pipe. The outlet of the mixer 5 is connected to the inlet of the flotation device 8 via a pipe. The mixer 5 is used to fully mix the produced water from the oilfield, the pretreatment agent added by the dosing module 20, and ozone to achieve ozone-enhanced premixed demulsification. A premixed water inlet valve 112 is installed on the first inlet of the mixer 5. The inlet of the premixed water inlet valve 112 is connected to the outlet pipe of the mixer 5 via a first through pipe 101. An air flotation water inlet valve 113 is installed on the first through pipe 101.

[0040] The ozone generator 4 is equipped with a first outlet, a second outlet, a third outlet and a fourth outlet. The first outlet of the ozone generator 4 is connected to the inlet of the mixer 5 through a pipe. A premixed ozone aeration valve 114 is installed on this pipe. Ozone is mainly used for ozone pre-oxidation demulsification in the premixed module 3. The strong oxidizing property of ozone can destroy the stable structure of emulsified oil, promote oil-water separation, and at the same time play a role in oxidizing and degrading some organic matter and sterilizing, effectively reducing the use of pretreatment agents such as demulsifiers, bactericides or oxidants.

[0041] The second outlet of the ozone generator 4 is connected to the aeration plate at the bottom of the flotation device 8 through a pipe. An ozone aeration valve 115 is installed on this pipe. In the flotation treatment module 6, ozone is mainly used to generate ozone microbubbles and utilize their surface activity to enhance the adhesion and separation of oil droplets. At the same time, it oxidizes and decomposes organic matter and emulsified oil in the water, improves the flotation removal efficiency, reduces the use of PAC, PAM and other chemicals, and reduces the amount of sludge generated.

[0042] The third outlet of the ozone generator 4 is connected to the aeration pipe in the ceramic flat membrane module 15 of the fine filtration module 13 via a pipe, on which a membrane ozone aeration valve 134 is installed.

[0043] The fourth outlet of the ozone generator 4 is connected to the backwash pipe of the fine filtration module 13 via a pipe. A membrane ozone backwash aeration valve 117 is installed on the pipe connecting the fourth outlet to the backwash pipe. Ozone is mainly used for backwashing of the ceramic flat sheet membrane in the fine filtration module 13. The ozone and aeration are combined to enhance the gas washing. The strong oxidizing properties of ozone decompose the organic matter and pollutants adsorbed on the membrane surface, thereby achieving efficient backwashing and regeneration of the membrane, reducing the use of backwashing agents, and extending the service life of the membrane.

[0044] The aeration plate of the flotation device 8 is made of nano-ceramic material. The aeration plate generates microbubbles, which increases the contact area between the bubbles and suspended solids and emulsified oil in the water, prolongs the residence time, and improves the flotation removal efficiency. An oil and sludge scraper is installed at the top of the flotation device 8. The outlet of the oil and sludge scraper is connected to the inlet of the oil recovery device 9 via a pipe. The oil and sludge scraper is used to collect the floating oil and sludge and send them to the oil recovery device 9. A sludge discharge port is located at the bottom of the flotation device 8. The sludge discharge port of the flotation device 8 is connected to the inlet of the sludge treatment device 7 via a pipe, and a flotation sludge discharge valve 116 is installed on this pipe.

[0045] The ozone generator 4 in the premix module 3, the flotation device 8 in the flotation treatment module 6, the aeration pipe in the ceramic flat sheet membrane module 15 of the fine filtration module 13, and the backwash pipe of the fine filtration module 13 are all connected to the ozone generator 4 through pipes, and the oxidation, demulsification, sterilization, and aeration effects of ozone are used to enhance the effect.

[0046] The outlet of the air flotation device 8 is connected to a three-way pipe. The first outlet of the three-way pipe is connected to the inlet of the first filter water inlet pump 202, and the second outlet of the three-way pipe is connected to the inlet of the second filter water inlet pump 203. A first-stage high-efficiency vortex filter inlet valve 119 is installed on the inlet of the first-stage high-efficiency vortex filter 11. The inlet of the first-stage high-efficiency vortex filter inlet valve 119 is connected to the outlet of the first filter water inlet pump 202 and the second through pipe 102 through pipes. An air flotation outlet valve 118 is installed on the second through pipe 102. The second through pipe 102 is connected to the inlet of the water storage tank module 19 through pipes. The outlet of the second filter water inlet pump 203 is connected to the inlet of the second-stage high-efficiency vortex filter 12 through the fifth through pipe 105. A second-stage high-efficiency vortex filter inlet valve 125 is installed on the fifth through pipe 105.

[0047] The outlet of the first-stage high-efficiency vortex filter 11 is connected to the outlet of the water storage tank module 19 via a first pipe. The first pipe is equipped with a backwash inlet valve 129 and a first backwash inlet pump 204. A third through pipe 103 is also connected to the outlet of the first-stage high-efficiency vortex filter 11, and the third through pipe 103 is connected to a fourth through pipe 104. A parallel outlet valve 126 for the first-stage high-efficiency vortex filter 126 is installed on the third through pipe 103. The inlet of the parallel outlet valve 126 is connected to the outlet of the inlet valve 125 for the second-stage high-efficiency vortex filter via a pipe. A series outlet valve 124 for the high-efficiency vortex filter 12 is installed on this pipe. The outlet of the second-stage high-efficiency vortex filter 12 is connected to the outlet of the water storage tank module 19 via a second pipe. The outlet of block 19 is connected to the second pipe, on which a backwash inlet valve 130 and a second backwash inlet pump 205 of the second-stage high-efficiency vortex filter are installed. A third pipe is provided on the second pipe between the backwash inlet valve 130 and the outlet of the second-stage high-efficiency vortex filter 12. The third pipe connects the second pipe to the fourth through pipe 104. A second-stage high-efficiency vortex filter outlet valve 127 is installed on the third pipe. A vortex filter outlet valve 122 is installed on the fourth through pipe 104. The outlet of the vortex filter outlet valve 122 is connected to the second through pipe 102. The inlet of the vortex filter outlet valve 122 is connected to the inlet of the filter tank 16 in the fine filtration module 13 through the fourth pipe. A membrane tank inlet valve 123 is installed on the fourth pipe.

[0048] The inlet of the backwash inlet valve 129 of the first-stage high-efficiency rotary bed filter is connected to the outlet of the backwash inlet valve 130 of the second-stage high-efficiency rotary bed filter through the fifth pipe. The fifth pipe is equipped with a series backwash valve 131 of the high-efficiency rotary bed filter.

[0049] Furthermore, the inlet water of the first-stage high-efficiency vortex filter 11 and the second-stage high-efficiency vortex filter 12 adopts cross-flow tangential inlet water to achieve vortex filtration. The first-stage high-efficiency vortex filter 11 and the second-stage high-efficiency vortex filter 12 are respectively provided with backwash outlets. A backwash outlet valve 120 is installed on the backwash outlet of the first-stage high-efficiency vortex filter 11, and a backwash outlet valve 121 is installed on the backwash outlet of the second-stage high-efficiency vortex filter 12. The backwash outlet valves 120 and 121 are connected to the return water port of the air flotation device 8 through pipelines.

[0050] like Figure 3 As shown, the filter tank 16 is provided with an oil discharge port, which is connected to the oil recovery device 9 through a pipe. The oil discharge device is used to discharge the floating oil intercepted by the ceramic membrane filter into the oil recovery device 9. The bottom of the filter tank 16 is provided with a sludge discharge port, which is connected to the sludge pump of the sludge treatment device 7 through a pipe. A membrane tank sludge discharge valve 128 is installed on this pipe.

[0051] like Figure 1 , 3 As shown, the permeate system 17 includes a membrane permeate pump 206 and a membrane permeate valve 132; the backwash system 18 includes a membrane backwash pump 207 and a membrane backwash valve 133; the aeration device includes an aeration blower 14; the membrane permeate pump 206 and the membrane permeate valve 132 are connected to the permeate pipe of the ceramic flat-plate membrane module 15 via permeate pipes; the membrane backwash pump 207 and the membrane backwash valve 133 are connected to the permeate pipe of the ceramic flat-plate membrane module 15 via backwash pipes; the permeate pipe and the backwash pipe are connected by a bypass; when the membrane produces water, the aeration system 17 is activated. When the membrane permeate valve 132 and membrane permeate pump 206, membrane backwash pump 207 and membrane backwash valve 133 are stopped, permeate water is discharged from the ceramic flat sheet membrane module 15 into the storage tank module 19. During membrane backwashing, the membrane backwash valve 133 and membrane backwash pump 207 are started, the membrane permeate pump 206 and membrane permeate valve 132 are closed, and water flows from the storage tank module 19 to the ceramic flat sheet membrane module 15. Permeate water and backwashing do not run simultaneously. The aeration blower 14 is connected to the aeration duct in the ceramic flat sheet membrane module 15 through a pipeline.

[0052] The dosing module 20 includes a pretreatment agent dosing device 21, a PAC dosing device 22, a PAM dosing device 23, a membrane acid washing dosing device 24, and a membrane alkali washing dosing device 25. Each dosing module 20 includes a metering dosing pump, a mixer, and a dosing tank.

[0053] The pretreatment agent dosing device 21 is connected to the third inlet of the mixer 5 in the premixing module 3 via a pipeline. The pretreatment agent in the pretreatment agent dosing device 21 includes demulsifiers, oxidants, or bactericides, selected according to the characteristics of the produced water quality in the oilfield. If the produced water inlet is highly emulsified and has a high oil content, a demulsifier is selected. If the produced water inlet contains a large number of bacteria, a bactericide is selected to control sulfate-reducing bacteria, saprophytic bacteria, and iron bacteria. If the produced water contains a large amount of sulfur and iron ions, an oxidant is selected to avoid the formation of hydrogen sulfide and iron precipitates. This not only oxidizes and enhances the premixing effect but also sterilizes and controls sulfate-reducing bacteria and iron bacteria.

[0054] The PAC dosing device 22 and PAM dosing device 23 are connected to the dosing port of the air flotation device 8 in the air flotation treatment module 6 via pipelines, and are used for dosing the air flotation device 8.

[0055] The membrane alkaline washing dosing device 25 and the membrane acid washing dosing device 24 are connected to the backwashing pipe of the ceramic flat plate membrane module 15 of the fine filtration module 13 through pipes, and are used to chemically wash the ceramic flat plate membrane module 15. The preferred alkaline washing agent is sodium hypochlorite, sodium hypochlorite + sodium hydroxide or persulfate and sodium hydroxide. The preferred acid washing agent is citric acid or citric acid + hydrochloric acid.

[0056] This invention also includes a modular control method for oilfield produced water, which utilizes the control of the opening and closing of valves and pumps in a modular oilfield produced water treatment system to achieve pipeline reconfiguration, specifically including the following steps:

[0057] S1. Detect the oil content and suspended solids content of the produced water and the influent, and adjust the opening and closing of valves and pumps accordingly;

[0058] Scenario 1: When the oil content of the influent is >1000 mg / L and the suspended solids content is >500 mg / L:

[0059] Specifically, it is for the treatment of produced water from oilfields with highly emulsified, high-oil-content, and high-suspended-solids influent;

[0060] At this point, the first type of pipeline reconstruction is achieved by controlling the opening and closing of valves and pumps, so that the primary sedimentation module 1, premixing module 3, air flotation treatment module 6, depth filtration module 10, and fine filtration module 13 are connected in series; the dosing system is activated, in which the pretreatment agent dosing device 21 adds demulsifier;

[0061] Specifically: the sludge discharge pump 201, the first filter inlet pump 202, the first backwash inlet pump 204, the membrane permeate pump 206, and the membrane backwash pump 207 are started in a coordinated manner, while the second filter inlet pump 203 and the second backwash inlet pump 205 are not started. Here, the coordinated start means that the first filter inlet pump 202 starts according to the flotation liquid level and begins to feed water; the first backwash inlet pump 204 starts according to the pressure difference and begins backwashing; the membrane permeate pump 206 starts according to the liquid level in the membrane tank, producing water at high liquid level and stopping the pump at low liquid level; the membrane backwash pump 207 starts on a timer or according to the transmembrane pressure difference, while maintaining the liquid level in the storage tank module at a high liquid level.

[0062] The following valves are activated and linked: sedimentation device sludge discharge valve 111, premixed water inlet valve 112, premixed ozone aeration valve 114, air flotation ozone aeration valve 115, air flotation sludge discharge valve 116, membrane ozone aeration valve 134, first-stage high-efficiency vortex filter inlet valve 119, first-stage high-efficiency vortex filter backwash outlet valve 120, second-stage high-efficiency vortex filter backwash outlet valve 121, membrane tank inlet valve 123, high-efficiency vortex filter series outlet valve 124, second-stage high-efficiency vortex filter outlet valve 127, first-stage high-efficiency vortex filter backwash inlet valve 129, high-efficiency vortex filter series backwash valve 131, membrane permeate valve 132, and membrane backwash valve 133; other valves are closed; all through pipes are not in use.

[0063] Scenario 2: When the oil content and suspended solids content of the influent are <200 mg / L and <200 mg / L respectively:

[0064] Specifically, it is for the treatment of produced water from oilfields with low oil content and low suspended solids as the influent.

[0065] At this time, controlling the opening and closing of valves and pumps realizes the second form of pipeline reconstruction, so that the primary sedimentation module 1, the air flotation treatment module 6, and the depth filtration module 10 are connected in series, and the first-stage high-efficiency rotary bed filter 11 and the second-stage high-efficiency rotary bed filter 12 in the depth filtration module 10 are operated in parallel; the pretreatment agent dosing device 21, the membrane acid washing dosing device 24, and the membrane alkali washing dosing device 25 are not activated, while the PAC dosing device 22 and the PAM dosing device 23 are activated.

[0066] Specifically: the following pumps are activated in a coordinated manner: sludge discharge pump 201, first filter inlet pump 202, second filter inlet pump 203, first backwash inlet pump 204, second backwash inlet pump 205, membrane permeate pump 206, and membrane backwash pump 207.

[0067] The following valves are activated and linked: sedimentation device sludge discharge valve 111, air flotation inlet valve 113, air flotation ozone aeration valve 115, air flotation sludge discharge valve 116, first-stage high-efficiency rotary bed filter inlet valve 119, first-stage high-efficiency rotary bed filter backwash outlet valve 120, second-stage high-efficiency rotary bed filter backwash outlet valve 121, rotary bed filter outlet valve 122, second-stage high-efficiency rotary bed filter inlet valve 125, first-stage high-efficiency rotary bed filter parallel outlet valve 126, second-stage high-efficiency rotary bed filter outlet valve 127, first-stage high-efficiency rotary bed filter backwash inlet valve 129, and second-stage high-efficiency rotary bed filter backwash inlet valve 130.

[0068] The premixed water inlet valve 112, premixed ozone aeration valve 114, membrane ozone aeration valve 134, air flotation outlet valve 118, membrane tank inlet valve 123, high-efficiency rotary bed filter series outlet valve 124, membrane tank sludge discharge valve 128, and high-efficiency rotary bed filter series backwash valve 131 are not activated, while the first through pipe 101, third through pipe 103, fourth through pipe 104, and fifth through pipe 105 are activated.

[0069] Scenario 3: When the oil content of the influent is 200–1000 mg / L and the suspended solids content is 200–500 mg / L:

[0070] This refers to the treatment of produced water from oilfields with conventional water quality as the influent.

[0071] At this point, controlling the opening and closing of valves and pumps achieves the third form of pipeline reconfiguration, forming a series connection of primary sedimentation module 1, premixing module 3, air flotation treatment module 6, and depth filtration module 10. The first-stage high-efficiency rotary bed filter 11 and the second-stage high-efficiency rotary bed filter 12 in the depth filtration module 10 operate in parallel. The pretreatment agent dosing device 21, PAC dosing device 22, and PAM dosing device 23 are turned on, while the membrane acid washing dosing device 24 and membrane alkali washing dosing device 25 are turned off. Among them, the pretreatment agent dosing device 21 adds demulsifier.

[0072] Specifically: the sludge pump 201, the first filter inlet pump 202, the second filter inlet pump 203, the first backwash inlet pump 204, the second backwash inlet pump 205, the membrane permeate pump 206, and the membrane backwash pump 207 are started in a coordinated manner;

[0073] Sedimentation device sludge discharge valve 111, premixed water inlet valve 112, premixed ozone aeration valve 114, air flotation ozone aeration valve 115, air flotation sludge discharge valve 116, first-stage high-efficiency vortex filter inlet valve 119, first-stage high-efficiency vortex filter backwash outlet valve 120, second-stage high-efficiency vortex filter backwash outlet valve 121, vortex filter outlet valve 122, second-stage high-efficiency vortex filter inlet valve 125, first-stage high-efficiency vortex filter parallel outlet valve 126, second-stage high-efficiency vortex filter outlet valve 127 The first-stage high-efficiency rotary bed filter backwash inlet valve 129, the second-stage high-efficiency rotary bed filter backwash inlet valve 130, the membrane permeate valve 132, and the membrane backwash valve 133 are activated and linked. The air flotation inlet valve 113, the membrane ozone aeration valve 134, the air flotation outlet valve 118, the membrane tank inlet valve 123, the high-efficiency rotary bed filter series outlet valve 124, the membrane tank sludge discharge valve 128, and the high-efficiency rotary bed filter series backwash valve 131 are not activated and linked. The third through pipe 103, the fourth through pipe 104, and the fifth through pipe 105 are activated.

[0074] S2. Detect the sulfur and iron ion content in the extracted water;

[0075] When the sulfur ion concentration is greater than 25 mg / L or the iron ion concentration is greater than 20 mg / L, sodium hypochlorite is added to the pretreatment agent dosing device. Sodium hypochlorite can be used as both an oxidant and a bactericide.

[0076] Specifically: the sludge pump 201, the first filter inlet pump 202, the second filter inlet pump 203, the first backwash inlet pump 204, the second backwash inlet pump 205, the membrane permeate pump 206, and the membrane backwash pump 207 are started in a coordinated manner;

[0077] The following valves are activated and linked: sedimentation device sludge discharge valve 111, premixed water inlet valve 112, premixed ozone aeration valve 114, air flotation ozone aeration valve 115, air flotation sludge discharge valve 116, first-stage high-efficiency vortex filter inlet valve 119, first-stage high-efficiency vortex filter backwash outlet valve 120, second-stage high-efficiency vortex filter backwash outlet valve 121, vortex filter outlet valve 122, second-stage high-efficiency vortex filter inlet valve 125, first-stage high-efficiency vortex filter parallel outlet valve 126, second-stage high-efficiency vortex filter outlet valve 127, first-stage high-efficiency vortex filter backwash inlet valve 129, second-stage high-efficiency vortex filter backwash inlet valve 130, membrane permeate valve 132, and membrane backwash valve 133.

[0078] The following valves are not activated: air flotation inlet valve 113, membrane ozone aeration valve 134, air flotation outlet valve 118, membrane tank inlet valve 123, high-efficiency rotary bed filter series outlet valve 124, membrane tank sludge discharge valve 128, and high-efficiency rotary bed filter series backwash valve 131. The third through pipe 103, the fourth through pipe 104, and the fifth through pipe 105 are activated.

[0079] Furthermore, in step S1 above, when the inlet flow rate of this device is less than or equal to the specified processing capacity of the high-efficiency rotary bed filter, both the first-stage high-efficiency rotary bed filter and the second-stage high-efficiency rotary bed filter can be activated individually and used separately, with the valves adjusted as follows.

[0080] A. If only the first-stage high-efficiency rotary bed filter is used, on the basis of the above, shut down the second filter inlet pump 203 and the second backwash inlet pump 205, and at the same time shut down the second-stage high-efficiency rotary bed filter backwash outlet valve 121, the second-stage high-efficiency rotary bed filter inlet valve 125, the second-stage high-efficiency rotary bed filter outlet valve 127 and the second-stage high-efficiency rotary bed filter backwash inlet valve 130, and deactivate the fifth through pipe 105.

[0081] B. If only the second-stage high-efficiency rotary bed filter is used, based on the above, shut down the first filter inlet pump 202 and the first backwash inlet pump 204, and simultaneously shut down the first-stage high-efficiency rotary bed filter inlet valve 119, the first-stage high-efficiency rotary bed filter backwash outlet valve 120, the first-stage high-efficiency rotary bed filter parallel outlet valve 126, and the first-stage high-efficiency rotary bed filter backwash inlet valve 129. The third through pipe 103 is also deactivated.

[0082] In case three of step S1 above, if the effluent requires an oil content of ≤2mg / L and a suspended solids content of ≤2mg / L, then the membrane tank inlet valve 123 is opened to add the fine filtration module 13 to the treatment process.

[0083] Example 1:

[0084] like Figure 4 As shown, the produced water from a certain oilfield has an oil content of 2500 mg / L, suspended solids of 800 mg / L, a high proportion of emulsified oil, high bacterial content, and no high sulfur / iron ion content. According to the method described in Case 1, the valves and pumps are adjusted to control the primary sedimentation module, premixing module, air flotation module, deep filtration module, and fine filtration module to be connected in series.

[0085] (1) Primary sedimentation module for primary sedimentation separation: the oilfield produced water is subjected to gravity sedimentation for primary sedimentation separation, with a residence time of 2.0h, to remove most of the free oil and large particles of mud and sand. The floating oil enters the oil recovery device for recycling, and the primary sedimentation sludge is discharged into the sludge treatment device for sludge treatment.

[0086] (2) Ozone-enhanced premixing: 50 mg / L of demulsifier, 120 mg / L of bactericide and 40 mg / L of ozone, which have been screened and confirmed by bottle test, are added to the effluent of the primary sedimentation module through the dosing device and the ozone generator respectively, and are thoroughly mixed. The demulsifier and ozone are used to destroy the stable structure of the emulsified oil to achieve ozone-enhanced premixing demulsification, while the bactericide and ozone are used to kill bacteria in the water.

[0087] (3) Ozone-enhanced flotation in the flotation treatment module: PAC 100mg / L and PAM 3mg / L are added to the flotation treatment module through the dosing device. Ozone microbubbles are generated by the ozone generator through the nano-ceramic aeration plate. The ozone concentration is 50mg / L and the flotation residence time is 30min. Ozone-enhanced flotation separation is achieved to remove suspended solids, emulsified oil, COD and other pollutants from the produced water. The floating oil and scum are discharged into the oil recovery device for oil recovery and utilization, and the flotation sludge is discharged into the sludge treatment device for sludge treatment.

[0088] (4) Deep filtration module performs multi-stage vortex bed deep filtration: The first-stage high-efficiency vortex bed filter with cross-flow water inlet design and the second-stage high-efficiency vortex bed filter are used for series filtration. The filter media particle sizes are 2~4mm, 0.8~2mm, 0.4~0.8mm and 0.2~0.4mm respectively. The filtration operation pressure difference is set to 0.9bar. When the set value is reached, backwashing begins and lasts for 15 minutes to remove suspended solids and oily pollutants from the water. The deep filtration effluent is divided into two paths. One path enters the ceramic flat sheet membrane system of the fine filtration module, and the other path is used as backwash water for the deep filtration module for recycling. If the activated filter media is severely contaminated, ozone is introduced into the backwash pipe for ozone-enhanced backwashing. The ozone dosage concentration is 2mg / L.

[0089] (5) Fine filtration module performs ceramic membrane fine filtration: membrane pore size 0.1μm, membrane design flux 40LMH, continuous aeration and gas washing, backwash ozone concentration 3mg / L, ozone addition frequency 1 time / h, water washing is carried out simultaneously, backwash time 2min, ceramic membrane chemical washing is prepared for use, of which alkaline washing is sodium hypochlorite 1500mg / L + NaOH 2000mg / L; acid washing is citric acid 15000mg / L.

[0090] After treatment by a multi-stage series process, the effluent suspended solids concentration is <1mg / L, oil content concentration is <1mg / L, and bacterial content is <100CFU / mL. All indicators are superior to the reinjection standard for ultra-low permeability formations.

[0091] Example 2:

[0092] The produced water from a certain oilfield has an oil content of 100 mg / L, suspended solids of 180 mg / L, and a low proportion of emulsified oil. According to the second scenario of this method, the valves and pumps are adjusted to open and close. After the valves and pumps are controlled, the process of this device is adjusted to be: primary sedimentation separation → ozone-enhanced flotation → multi-stage vortex bed parallel deep filtration → effluent reinjection, with ceramic membrane fine filtration as a backup unit.

[0093] (1) Primary sedimentation module for primary sedimentation separation: the oilfield produced water is subjected to gravity sedimentation for primary sedimentation separation, with a residence time of 2.0h, to remove most of the free oil and large particles of mud and sand. The floating oil enters the oil recovery device for recycling, and the primary sedimentation sludge is discharged into the sludge treatment device for sludge treatment.

[0094] (2) Ozone-enhanced flotation in the flotation treatment module: PAC 30mg / L and PAM 1.5mg / L are added to the flotation treatment module through the dosing device. Ozone microbubbles are generated by the ozone generator through the nano-ceramic plate. The ozone concentration is 20mg / L and the flotation residence time is 20min to achieve ozone-enhanced flotation separation, remove suspended solids, emulsified oil, COD and other pollutants from the produced water. The floating oil and scum are discharged into the oil recovery device for oil recovery and utilization, and the flotation sludge is discharged into the sludge treatment device for sludge treatment.

[0095] (3) Deep filtration module performs vortex deep filtration: a first-stage high-efficiency vortex filter with cross-flow inlet design and a second-stage high-efficiency vortex filter are used for parallel filtration. The filter media particle sizes are 2~4mm, 0.8~2mm, 0.4~0.8mm and 0.2~0.4mm respectively. The filtration operating pressure difference is set to 0.9bar. When the set value is reached, backwashing begins and lasts for 10 minutes to efficiently remove suspended solids and oily pollutants from the water. The deep filtration effluent is divided into two paths. One path enters the ceramic flat sheet membrane system, and the other path is used as backwash water for the deep filtration module for recycling. If the activated filter media is severely contaminated, ozone is introduced into the backwash pipe for ozone-enhanced backwashing. The ozone dosage concentration is 1mg / L.

[0096] After treatment, the concentration of suspended solids in the effluent is <5 mg / L, and the concentration of oil content is <5 mg / L, meeting the standards for conventional formation reinjection.

[0097] Example 3:

[0098] The produced water from a certain oilfield has an oil content of 800 mg / L, suspended solids of 400 mg / L, S2- concentration of 30 mg / L, and Fe2+ concentration of 25 mg / L. Following the method described in section three, the valves and pumps are adjusted to open and close. After controlling the valves and pumps, the process flow of this unit is adjusted as follows: primary sedimentation separation → ozone-enhanced premixing → ozone-enhanced flotation → multi-stage parallel rotary bed deep filtration → ceramic membrane fine filtration → effluent reinjection.

[0099] (1) Primary sedimentation module for primary sedimentation separation: the oilfield produced water is subjected to gravity sedimentation for primary sedimentation separation, with a residence time of 2.0h, to remove most of the free oil and large particles of mud and sand. The floating oil enters the oil recovery device for recycling, and the primary sedimentation sludge is discharged into the sludge treatment device for sludge treatment.

[0100] (2) Ozone-enhanced premixing: 30 mg / L of demulsifier, 50 mg / L of sodium hypochlorite oxidant and 40 mg / L of ozone, which have been confirmed by bottle test screening, are added to the effluent of the primary sedimentation module through the dosing device and the ozone generator respectively, and are thoroughly mixed. The demulsifier and ozone are used to destroy the stable structure of the emulsified oil to achieve ozone-enhanced premixing demulsification. At the same time, the oxidant and ozone are used to achieve the oxidation and removal of S2- and Fe2+.

[0101] (3) Ozone-enhanced flotation in the flotation treatment module: PAC 50mg / L and PAM 2.5mg / L are added to the flotation treatment module through the dosing device. Ozone microbubbles are generated by the ozone generator through the nano-ceramic aeration plate. The ozone concentration is 40mg / L and the flotation residence time is 25min. Ozone-enhanced flotation separation is achieved to remove suspended solids, emulsified oil, COD and other pollutants from the produced water. The floating oil and scum are discharged into the oil recovery device for oil recovery and utilization, and the flotation sludge is discharged into the sludge treatment device for sludge treatment.

[0102] (4) Deep filtration module performs multi-stage vortex bed parallel deep filtration: The first-stage high-efficiency vortex bed filter with cross-flow water inlet design and the second-stage high-efficiency vortex bed filter are used for parallel filtration. The filter media particle sizes are 2~4mm, 0.8~2mm, 0.4~0.8mm and 0.2~0.4mm respectively. The filtration operation pressure difference is set to 0.9bar. When the set value is reached, backwashing begins and lasts for 15 minutes to efficiently remove suspended solids and oily pollutants from the water. The deep filtration effluent is divided into two paths. One path enters the ceramic flat sheet membrane system, and the other path is used as backwash water for the deep filtration module for recycling. If the activated filter media is severely contaminated, ozone is introduced into the backwash pipe for ozone-enhanced backwashing. The ozone dosage concentration is 2mg / L.

[0103] (5) Fine filtration module performs fine filtration with ceramic membrane: The pore size of the ceramic flat sheet membrane module is 0.1 μm, the membrane design flux is 50 LMH, continuous aeration and gas washing, backwash ozone concentration is 2 mg / L, ozone addition frequency is 1 time / h, water washing is carried out simultaneously, backwash time is 2 min, and the ceramic membrane is prepared for chemical washing, of which the alkaline washing is sodium hypochlorite 1000 mg / L; the acid washing is citric acid 10000 mg / L.

[0104] After treatment, the concentration of suspended solids in the effluent is <2mg / L, the concentration of oil content is <2mg / L, and all indicators meet the reinjection standards.

[0105] The above are merely preferred embodiments of the present invention and do not limit the patent scope of the present invention. Any equivalent structural transformations made under the concept of the present invention using the description and drawings of the present invention, or direct / indirect applications in other related technical fields, are included within the patent protection scope of the present invention.

Claims

1. A modular treatment system for oilfield produced water, characterized in that: The system comprises a primary sedimentation module, a premixing module, an air flotation module, a deep filtration module, and a fine filtration module, connected in series via pipelines. The outlets of the deep filtration and fine filtration modules are connected to a storage tank module via pipelines. The dosing ports of the premixing, air flotation, and fine filtration modules are connected to a dosing module via pipelines. Valves are installed on the pipelines connecting each module. The primary sedimentation module includes at least one stage of sedimentation device. The premixing module includes a mixer and an ozone generator, which is connected to the mixer, air flotation module, and fine filtration module via pipelines. The air flotation module includes an air flotation device, an oil recovery device, and a sludge treatment device. The deep filtration module includes a first-stage high-efficiency vortex filter and a second-stage high-efficiency vortex filter, which are connected via pipelines and valves and can be switched between parallel, series, and individual operation. The fine filtration module includes a ceramic membrane filter, which includes a filter tank and a ceramic flat sheet membrane system installed within the filter tank.

2. The modular treatment system for produced water in oilfields according to claim 1, characterized in that: The settling device includes a produced water outlet, an oil outlet, and a settling sludge outlet. A sludge discharge valve is installed on the settling sludge outlet. The oil outlet is connected to the oil inlet of the oil recovery device of the air flotation treatment module through a pipeline. The outlet of the settling device sludge discharge valve is connected to the inlet of the sludge discharge pump through a pipeline. The outlet of the sludge discharge pump is connected to the inlet of the sludge treatment device of the air flotation treatment module through a pipeline.

3. The modular treatment system for produced water in oilfields according to claim 2, characterized in that: The mixer is provided with a first inlet, a second inlet and a third inlet. The first inlet of the mixer is connected to the outlet of the sedimentation device through a pipe, the second inlet is connected to the outlet of the ozone generator through a pipe, and the third inlet is connected to the outlet of the dosing module through a pipe. The outlet of the mixer is connected to the inlet of the flotation device through a pipe. A premixed water inlet valve is installed on the first inlet of the mixer. The inlet of the premixed water inlet valve is connected to the outlet pipe of the mixer through a first through pipe. An air flotation water inlet valve is installed on the first through pipe.

4. The modular oilfield produced water treatment system according to claim 3, characterized in that: The ozone generator has a first outlet, a second outlet, a third outlet, and a fourth outlet. The first outlet of the ozone generator is connected to the inlet of the mixer via a pipe, and a premixed ozone aeration valve is installed on this pipe. The second outlet of the ozone generator is connected to the aeration plate at the bottom of the air flotation device via a pipe, and an air flotation ozone aeration valve is installed on this pipe. The third outlet of the ozone generator is connected to the aeration duct in the ceramic flat sheet membrane module of the fine filtration module via a pipe, and a membrane ozone aeration valve is installed on this pipe. The fourth outlet of the ozone generator is connected to the backwash pipe of the fine filtration module via a pipe, and a membrane ozone backwash aeration valve is installed on this pipe.

5. The modular oilfield produced water treatment system according to claim 4, characterized in that: The air flotation unit is equipped with an oil and sludge scraper at the top, and the outlet of the oil and sludge scraper is connected to the inlet of the oil recovery unit through a pipe. The air flotation unit has a sludge discharge port at the bottom, which is connected to the inlet of the sludge treatment unit through a pipe. An air flotation sludge discharge valve is installed on this pipe. The outlet of the air flotation unit is connected to a three-way pipe. The first outlet of the three-way pipe is connected to the inlet of the first filter inlet pump, and the second outlet of the three-way pipe is connected to the inlet of the second filter inlet pump. A first-stage high-efficiency rotary bed filter inlet valve is installed at the inlet of the first-stage high-efficiency rotary bed filter. The inlet of the first-stage high-efficiency rotary bed filter inlet valve is connected to the outlet of the first filter inlet pump and the second through pipe through pipes. An air flotation outlet valve is installed on the second through pipe, which is connected to the inlet of the storage tank module through a pipe. The outlet of the second filter inlet pump is connected to the inlet of the second-stage high-efficiency rotary bed filter through a fifth through pipe, which is also equipped with a second-stage high-efficiency rotary bed filter inlet valve.

6. The modular treatment system for produced water in oilfields according to claim 5, characterized in that: A third through pipe is installed at the outlet of the first-stage high-efficiency vortex filter, which is connected to a fourth through pipe. A parallel outlet valve for the first-stage high-efficiency vortex filter is installed on the third through pipe. The inlet of the parallel outlet valve for the first-stage high-efficiency vortex filter is connected to the inlet of the second-stage high-efficiency vortex filter via a pipe. A series outlet valve for the high-efficiency vortex filter is installed on this pipe. A third pipe is installed at the outlet of the second-stage high-efficiency vortex filter, which is connected to a fourth through pipe. An outlet valve for the second-stage high-efficiency vortex filter is installed on the third pipe. An outlet valve for the vortex filter is installed on the fourth through pipe. The outlet of the vortex filter outlet valve is connected to the second through pipe. The inlet of the vortex filter outlet valve is connected to the inlet of the filter tank in the fine filtration module via the fourth pipe. A membrane tank inlet valve is installed on the fourth pipe.

7. The modular oilfield produced water treatment system according to claim 6, characterized in that: The outlet of the first-stage high-efficiency rotary bed filter is connected to the outlet of the water storage tank module through the first pipe. The first pipe is equipped with the backwash inlet valve and the first backwash inlet pump of the first-stage high-efficiency rotary bed filter. The outlet of the second-stage high-efficiency rotary bed filter is connected to the outlet of the water storage tank module through the second pipe. The second pipe is equipped with the backwash inlet valve and the second backwash inlet pump of the second-stage high-efficiency rotary bed filter. The inlet of the backwash inlet valve of the first-stage high-efficiency rotary bed filter is connected to the outlet of the backwash inlet valve of the second-stage high-efficiency rotary bed filter through the fifth pipe. The fifth pipe is equipped with a series backwash valve of the high-efficiency rotary bed filter. The first-stage high-efficiency vortex filter and the second-stage high-efficiency vortex filter are each equipped with a backwash outlet. The backwash outlet of the first-stage high-efficiency vortex filter is equipped with a backwash outlet valve, and the backwash outlet of the second-stage high-efficiency vortex filter is equipped with a backwash outlet valve. The backwash outlet valves of the first-stage high-efficiency vortex filter and the second-stage high-efficiency vortex filter are connected to the return water port of the air flotation device through pipelines.

8. The modular treatment system for produced water in oilfields according to claim 7, characterized in that: The filter tank is equipped with an oil discharge port, which is connected to an oil recovery device via a pipeline. The oil discharge device is used to discharge the floating oil intercepted by the ceramic membrane filtration into the oil recovery device. The bottom of the filter tank is equipped with a sludge discharge port, which is connected to the sludge discharge pump of the sludge treatment device via a pipeline. A membrane tank sludge discharge valve is installed on this pipeline.

9. The modular treatment system for produced water in oilfields according to claim 8, characterized in that: The dosing module includes a pretreatment agent dosing device, a PAC dosing device, a PAM dosing device, a membrane acid washing dosing device, and a membrane alkali washing dosing device. The pretreatment agent dosing device is connected to the third inlet of the mixer in the premixing module via a pipeline. The PAC dosing device and the PAM dosing device are connected to the flotation device dosing port in the flotation treatment module via pipelines. The membrane alkali washing dosing device and the membrane acid washing dosing device are connected to the ceramic flat sheet membrane system of the fine filtration module via pipelines.

10. A modular control method for oilfield produced water, used to control the opening and closing of valves and pumps in the modular treatment system for oilfield produced water as described in claim 9, to achieve pipeline reconfiguration, characterized in that: Specifically, the steps include the following: S1. Detect the oil content and suspended solids content of the extracted water, and adjust the opening and closing of valves and pumps accordingly; Scenario 1: When oil content > 1000 mg / L and suspended solids content > 500 mg / L: The opening and closing of valves and pumps are controlled to achieve the first form of pipeline reconstruction, so that the primary sedimentation module, premixing module, air flotation treatment module, deep filtration module, and fine filtration module are connected in series; the dosing system is activated, and the pretreatment agent dosing device adds demulsifier; Scenario 2: When oil content < 200 mg / L and suspended solids content < 200 mg / L: The second form of pipeline reconfiguration is achieved by controlling the opening and closing of valves and pumps, so that the primary sedimentation module, air flotation treatment module, and deep filtration module are connected in series, and the first-stage high-efficiency rotary bed filter and the second-stage high-efficiency rotary bed filter in the deep filtration module are operated in parallel; the pretreatment agent dosing device, membrane acid washing dosing device, and membrane alkali washing dosing device are not activated, while the PAC dosing device and PAM dosing device are activated. Scenario 3: When the oil concentration is 200–1000 mg / L and the suspended solids content is 200–500 mg / L: The opening and closing of valves and pumps are controlled to achieve the third form of pipeline reconfiguration, forming a primary sedimentation module, a premixing module, an air flotation treatment module, and a deep filtration module connected in series. The first-stage high-efficiency rotary bed filter and the second-stage high-efficiency rotary bed filter in the deep filtration module are connected in parallel. The pretreatment agent dosing device, PAC dosing device, and PAM dosing device are turned on, while the membrane acid washing dosing device and the membrane alkali washing dosing device are turned off. S2. Detect the sulfur and iron ion content in the extracted water; When the sulfide ion concentration is >25 mg / L or the iron ion concentration is >20 mg / L, sodium hypochlorite is added to the pretreatment agent dosing device.

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