Deep treatment and recycling system and method for offshore heavy oil thermal recovery produced water

Abstract

The invention relates to an advanced treatment and recycling system and method for offshore heavy oil thermal recovery produced water. The system comprises an ultrafiltration unit, a reverse osmosis unit, a strong brine recycling unit and a first water producing tank, the liquid inlet end of the ultrafiltration unit is used for being communicated with the liquid outlet end of the offshore heavy oil thermal recovery produced water pretreatment unit, and the liquid outlet end of the ultrafiltration unit is communicated with the liquid inlet end of the reverse osmosis unit; the produced water outlet end of the reverse osmosis unit is communicated with the water inlet end of the first produced water tank, and the water outlet end of the first produced water tank is communicated with an external recycling system; the bottom of the first water producing tank is higher than the top of the reverse osmosis unit, and clear liquid in the first water producing tank can flow back to the reverse osmosis unit; the concentrated water outlet end of the reverse osmosis unit is communicated with the liquid inlet end of the strong brine recycling unit, and the liquid outlet end of the strong brine recycling unit is communicated with the liquid inlet end of the reverse osmosis unit. Clear liquid penetrates through the surface of the membrane to reach the concentrated water side by utilizing the osmotic pressure on the two sides of the membrane and the pressure difference of the high-position first water producing tank to wash away pollutants in the pore diameter of the membrane, so that the self-cleaning of the reverse osmosis membrane is completed.

Description

Technical Field

[0001] The present invention relates to the technical field of water treatment, and in particular to a system and method for deep treatment and reuse of produced water from offshore heavy oil thermal recovery. Background Art

[0002] In the process of offshore heavy oil thermal recovery, the treatment of thermal recovery produced water is particularly important because offshore platform operations are difficult and offshore heavy oil recovery is a long-term process. Therefore, the sustainable use of water resources can effectively save operating costs. By recycling thermal recovery produced water to the boiler system or other recycling systems, it is not only possible to achieve the rational use of resources, but also to maintain the long-term stable operation of the mining operation.

[0003] At present, in the treatment system of produced water from offshore heavy oil thermal recovery, the produced water is mainly filtered by ultrafiltration membrane method, and then desalted by reverse osmosis membrane method. However, pollutants will remain on the membrane surface, which will affect the service life of the membrane layer and the treatment effect of produced water from thermal recovery under long-term operation, and then affect the reuse of produced water to the boiler system or other reuse systems. Therefore, it is necessary to comprehensively consider factors such as cost, efficiency, and energy saving, and provide an offshore heavy oil thermal recovery produced water deep treatment and reuse system that can operate stably for a long time, which is crucial for the effective operation of offshore heavy oil thermal recovery. Summary of the invention

[0004] In view of this, the main purpose of the present invention is to provide an offshore heavy oil thermal recovery produced water deep treatment and reuse system with reliable equipment, high degree of automation, and capable of effectively cleaning the reverse osmosis membrane, so as to solve the problem of pollutants remaining on the surface of the reverse osmosis membrane and causing membrane pollution.

[0005] In a first aspect, an embodiment of the present application provides a system for deep treatment and reuse of produced water from thermal recovery of offshore heavy oil, comprising an ultrafiltration unit, a reverse osmosis unit, a concentrated brine reuse unit, and a first produced water tank;

[0006] The liquid inlet of the ultrafiltration unit is used to communicate with the liquid outlet of the offshore heavy oil thermal recovery produced water pretreatment unit, and the liquid outlet of the ultrafiltration unit is communicated with the liquid inlet of the reverse osmosis unit;

[0007] The water outlet of the reverse osmosis unit is connected to the water inlet of the first water production tank, and the water outlet of the first water production tank is used to communicate with an external recycling system; and the bottom of the first water production tank is arranged higher than the top of the reverse osmosis unit, and the clear liquid in the first water production tank can flow back to the reverse osmosis unit;

[0008] The concentrated water outlet of the reverse osmosis unit is communicated with the liquid inlet of the concentrated brine recycling unit, and the liquid outlet of the concentrated brine recycling unit is communicated with the liquid inlet of the reverse osmosis unit.

[0009] In some of these embodiments, a pre-processing unit is further included;

[0010] The pretreatment unit comprises a raw water tank, a pretreatment pump, a pretreatment device and a pretreatment water production tank which are connected in sequence;

[0011] The liquid outlet of the pre-treatment water production tank is communicated with the liquid inlet of the ultrafiltration unit.

[0012] In some embodiments, the ultrafiltration unit includes an ultrafiltration boost pump, a security filter, an ultrafiltration water inlet valve, an ultrafiltration device, an ultrafiltration water production valve and a back pressure valve which are connected in sequence;

[0013] The liquid inlet end of the ultrafiltration lift pump is communicated with the liquid outlet end of the offshore heavy oil thermal recovery produced water pretreatment unit, and the liquid outlet end of the back pressure valve is communicated with the liquid inlet end of the reverse osmosis unit.

[0014] In some of these embodiments, the ultrafiltration unit further comprises an upper row valve, a lower row valve, and an air inlet valve;

[0015] The inlet of the upper row valve is communicated with the upper row port of the ultrafiltration device, the inlet of the lower row valve is communicated with the lower row port of the ultrafiltration device, and the outlets of the upper row valve and the lower row valve are both used to communicate with the ditch;

[0016] The inlet of the air intake valve is used to input ultrafiltration air intake, and the outlet of the air intake valve is communicated with the air intake of the ultrafiltration device.

[0017] In some of these embodiments, an ultrafiltration backwash unit is also included;

[0018] The ultrafiltration backwash unit comprises a water replenishment valve, a backwash water tank, a backwash pump, an ultrafiltration backwash filter and a backwash water inlet valve which are connected in sequence;

[0019] The water supply valve is arranged between the liquid outlet of the ultrafiltration unit and the liquid inlet of the backwash water tank;

[0020] The backwash water inlet valve is arranged between the liquid outlet end of the ultrafiltration backwash filter and the backwash liquid inlet end of the ultrafiltration unit.

[0021] In some embodiments, the reverse osmosis unit includes a reverse osmosis device and a reverse osmosis water production valve;

[0022] The liquid inlet of the reverse osmosis device is connected to the liquid outlet of the ultrafiltration unit, the water outlet of the reverse osmosis device is connected to the liquid inlet of the reverse osmosis water production valve, and the liquid outlet of the reverse osmosis water production valve is used to flow out the clear liquid produced by the reverse osmosis device;

[0023] The reverse osmosis device is connected to the first water production tank through a pipeline, and a self-cleaning water inlet valve is provided on the pipeline;

[0024] The number of the reverse osmosis devices is less than the number of the ultrafiltration devices, and the number of the ultrafiltration devices is at least two sets.

[0025] In some of the embodiments, a variable frequency high pressure pump is provided between the ultrafiltration unit and the reverse osmosis unit, and an RO water inlet valve is also provided between the variable frequency high pressure pump and the ultrafiltration unit.

[0026] In some embodiments, the concentrated brine recycling unit includes a salt return valve, a concentrated brine tank, a brine pump, a concentrated brine filter and a salt inlet valve which are sequentially connected;

[0027] The salt return valve is arranged between the concentrated water outlet of the reverse osmosis unit and the concentrated water inlet of the concentrated brine tank;

[0028] The salt inlet valve is arranged between the liquid outlet end of the concentrated salt water filter and the liquid inlet end of the reverse osmosis unit.

[0029] In some of the embodiments, a second produced water tank, a concentrate valve and a concentrate discharge valve are also included;

[0030] The water inlet end of the second water production tank is connected to the liquid outlet end of the reverse osmosis water production valve, and the water outlet end of the second water production tank is used to communicate with an external reuse system;

[0031] The liquid inlet end of the concentrated water valve is connected to the concentrated water outlet end of the reverse osmosis unit, and the liquid outlet end of the concentrated water valve is used to connect to an external processing device;

[0032] The liquid inlet end of the concentrated water discharge valve is communicated with the concentrated water outlet end of the reverse osmosis unit, and the liquid outlet end of the concentrated water discharge valve is used to communicate with the ditch.

[0033] In a second aspect, an embodiment of the present application provides a method for deep treatment and reuse of produced water from thermal recovery of offshore heavy oil, which is implemented by using any of the above-mentioned systems for deep treatment and reuse of produced water from thermal recovery of offshore heavy oil, and includes the following steps:

[0034] The pre-treated produced water from thermal recovery of offshore heavy oil is subjected to ultrafiltration treatment to obtain ultrafiltration produced water;

[0035] After the ultrafiltration water is subjected to reverse osmosis treatment, a clear liquid and concentrated water are obtained respectively; among which, a part of the clear liquid is recycled to the external recycling system, and the other part of the clear liquid is stored in the high-position first water production tank to be returned to the clear water side of the membrane during self-cleaning of the reverse osmosis membrane, and cooperated with the concentrated water returned to the concentrated water side of the membrane to clean the membrane.

[0036] Technical effects of the present invention:

[0037] 1. The present invention connects the concentrated water outlet of the reverse osmosis unit with the inlet of the concentrated brine recycling unit, and the outlet of the concentrated brine recycling unit with the inlet of the reverse osmosis unit; the produced water outlet of the reverse osmosis unit is connected with the inlet of the first produced water tank, and the clear liquid in the first produced water tank can flow back to the reverse osmosis unit, so that the reverse osmosis unit can use its self-produced clear liquid and concentrated brine to complete the self-cleaning of the reverse osmosis membrane, so as to ensure that the contaminated reverse osmosis membrane can restore normal performance. It not only improves the efficiency of water resource utilization, but also prevents the introduction of external pollution sources from causing pollution to the reverse osmosis unit, which meets the demand for rational utilization of resources in the process of producing water treatment of offshore heavy oil thermal recovery.

[0038] 2. The bottom of the first water production tank of the present invention is arranged higher than the top of the reverse osmosis unit in the height direction, and the osmotic pressure on both sides of the membrane and the pressure difference of the high-position first water production tank can be used to make the clear liquid pass through the membrane surface to the concentrated water side, flush away the pollutants in the membrane pores, and disperse the bacterial groups in the dead corners of the concentrated water side, so as to complete the self-cleaning of the reverse osmosis membrane. The entire system does not need to set any booster pump between the reverse osmosis unit and the first water production tank. The clear liquid in the first water production tank can naturally flow into the clear liquid side of the reverse osmosis unit by its own gravity and provide a certain pressure, so as to clean the pollutants on the membrane and reduce the system operation and maintenance costs.

[0039] 3. There is no need to set an intermediate water tank or filter between the ultrafiltration unit and the reverse osmosis unit of the present invention, which effectively reduces the cost of the equipment and also reduces the floor space, that is, reduces the space occupied by the offshore platform operation, and can provide operating space for other equipment according to actual needs, which is conducive to improving production efficiency. At the same time, the water filtered by ultrafiltration is directly used for reverse osmosis desalination without intermediate residence time, which reduces the occurrence of flocculation after the ultrafiltration unit and reduces the probability of reverse osmosis fouling.

[0040] Further features and aspects of the present disclosure will become apparent from the following detailed description of exemplary embodiments with reference to the attached drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate exemplary embodiments, features, and aspects of the disclosure and, together with the description, serve to explain the principles of the disclosure.

[0042] Figure 1 A schematic diagram of the structure of a system for deep treatment and reuse of produced water from thermal recovery of offshore heavy oil according to an embodiment of the present application is shown;

[0043] Figure 2 Shown is a schematic diagram of the composition of an ultrafiltration unit and a reverse osmosis unit according to an embodiment of the present application. DETAILED DESCRIPTION

[0044] Various exemplary embodiments, features and aspects of the present disclosure will be described in detail below with reference to the accompanying drawings. The same reference numerals in the accompanying drawings represent elements with the same or similar functions. Although various aspects of the embodiments are shown in the accompanying drawings, the drawings are not necessarily drawn to scale unless otherwise specified.

[0045] The word “exemplary” is used exclusively herein to mean “serving as an example, example, or illustration.” Any embodiment described herein as “exemplary” is not necessarily to be construed as preferred or advantageous over other embodiments.

[0046] In addition, in order to better illustrate the present disclosure, numerous specific details are given in the following specific embodiments. It should be understood by those skilled in the art that the present disclosure can also be implemented without certain specific details. In some examples, methods, means, components and circuits well known to those skilled in the art are not described in detail in order to highlight the subject matter of the present disclosure.

[0047] Embodiment 1

[0048] The embodiment of the present application provides a system for deep treatment and reuse of produced water from thermal recovery of offshore heavy oil, Figure 1 is a structural schematic diagram of a system for deep treatment and reuse of produced water from thermal recovery of offshore heavy oil according to an embodiment of the present application, such as Figure 1 As shown, the offshore heavy oil thermal recovery produced water deep treatment and reuse system comprises an ultrafiltration unit 100, a reverse osmosis unit 200, a concentrated brine reuse unit 300 and a first produced water tank 400; the liquid inlet end of the ultrafiltration unit 100 is used to communicate with the liquid outlet end of the offshore heavy oil thermal recovery produced water pretreatment unit 700, and the liquid outlet end of the ultrafiltration unit 100 is communicated with the liquid inlet end of the reverse osmosis unit 200; the produced water outlet end of the reverse osmosis unit 200 is communicated with the water inlet end of the first produced water tank 400, and the water outlet end of the first produced water tank 400 is used to communicate with an external reuse system; the bottom of the first produced water tank 400 is arranged higher than the top of the reverse osmosis unit 200, and the clear liquid in the first produced water tank 400 can flow back to the reverse osmosis unit 200; the concentrated water outlet end of the reverse osmosis unit 200 is communicated with the liquid inlet end of the concentrated brine reuse unit 300, and the liquid outlet end of the concentrated brine reuse unit 300 is communicated with the liquid inlet end of the reverse osmosis unit 200.

[0049] In this embodiment, after the produced water from offshore heavy oil thermal recovery passes through the ultrafiltration unit 100 and the reverse osmosis unit 200 in sequence, the corresponding concentrated water and clear liquid are produced. Among them, the concentrated water flows into the concentrated brine reuse unit 300, and part of the clear liquid flows into the first water production tank 400, so that when the reverse osmosis unit 200 needs to be cleaned, it can use its own clear liquid and concentrated brine to reflux to complete the self-cleaning of the reverse osmosis membrane, so as to ensure that the contaminated reverse osmosis membrane can restore normal performance, thereby ensuring the stable and long-term operation of the entire system. At the same time, the produced clear liquid can be reused to the external reuse system to achieve the rational use of resources. Here, it should be noted that the external reuse system in this embodiment includes a boiler system, or other reuse systems that require clear liquid, which can be reasonably applied according to actual use requirements. It should also be noted that the water temperature of the produced water from the offshore heavy oil thermal recovery in this embodiment is 60-90° C., the oil content is ≥1000 mg / L, the salt content is 15000-60000 mg / L, and the clear liquid filtered out by the reverse osmosis unit 200, that is, the clear liquid flowing into the first production water tank 400, has an oil content of ≤1 mg / L and a salt content of ≤1000 mg / L.

[0050] Specifically, the liquid inlet of the brine recycling unit 300 of this embodiment is connected to the brine outlet of the reverse osmosis unit 200, so that the brine generated when the system is automatically running can be stored in the brine recycling unit 300, and the liquid outlet of the brine recycling unit 300 is connected to the liquid inlet of the reverse osmosis unit 200, so that the brine produced by the reverse osmosis unit 200 can flow back to the brine side of the reverse osmosis unit 200 when the system needs to be self-cleaned. That is, during the cleaning process of the reverse osmosis unit 200, there is no need to connect other external brine or add chemical cleaning agents, and the brine produced by the reverse osmosis unit 200 can be used for reflux. On the one hand, it can improve the utilization efficiency of water resources, and on the other hand, it can reduce the dependence on chemical cleaning agents, and will not introduce new pollution sources to pollute the reverse osmosis membrane, maintain the performance stability of the reverse osmosis membrane, and meet the needs of rational utilization of resources in the process of producing water treatment of offshore heavy oil thermal recovery.

[0051] In addition, the water outlet of the reverse osmosis unit 200 of this embodiment is connected to the water inlet of the first water production tank 400. When the system is operating normally, part of the clear liquid filtered out by the reverse osmosis unit 200 enters the first water production tank 400 for storage, so as to be used for self-cleaning of the reverse osmosis unit 200. When the reverse osmosis unit 200 needs to be self-cleaned, the clear liquid in the first water production tank 400, i.e., the cleaning water tank, will flow back to the water outlet of the reverse osmosis unit 200, i.e., the clear liquid side, through the water inlet provided thereon, and flow to the concentrated water side. Here, it should be noted that the bottom of the first water production tank 400 of this embodiment is arranged higher than the top of the reverse osmosis unit 200 in the height direction, so that the clear liquid can pass through the membrane surface to the concentrated water side by utilizing the osmotic pressure on both sides of the membrane and the pressure difference of the high-position first water production tank 400, flushing away the pollutants in the membrane pore diameter, and dispersing the bacterial clusters in the dead corner of the concentrated water side, so as to complete the self-cleaning of the reverse osmosis membrane. The entire system does not need to set any booster pump between the reverse osmosis unit 200 and the first water production tank 400. The clear liquid in the first water production tank 400 can naturally flow into the clear liquid side of the reverse osmosis unit 200 by its own gravity and provide a certain pressure to achieve the cleaning of pollutants on the membrane and reduce the system operation and maintenance costs. The water outlet of the first water production tank 400 can also be connected to an external boiler system or other reuse system to supply the clear liquid filtered out by the reverse osmosis unit 200 to the boiler system or other reuse system to feed water, thereby increasing the comprehensive utilization efficiency of water resources.

[0052] It should also be noted that there is no need to set up an intermediate water tank or filter between the ultrafiltration unit 100 and the reverse osmosis unit 200 in this embodiment. The produced water after ultrafiltration directly enters the reverse osmosis unit 200 for treatment, which effectively reduces the cost investment in the equipment, reduces power consumption, and reduces the floor space. At the same time, since the produced water from thermal recovery is directly sent to the reverse osmosis desalination after ultrafiltration filtration, there is no intermediate residence time, which reduces the occurrence of post-flocculation in the ultrafiltration produced water tank, and directly reduces the probability of reverse osmosis fouling. In addition, the produced water after ultrafiltration directly enters the reverse osmosis desalination, which shortens the bacterial growth time and can reduce the amount of bactericide added to the reverse osmosis inlet.

[0053] In some of the embodiments, a pretreatment unit 700 is further included; the pretreatment unit 700 includes a raw water tank 710, a pretreatment pump 720, a pretreatment device 730 and a pretreatment water production tank 740 which are connected in sequence; the liquid outlet of the pretreatment water production tank 740 is connected to the liquid inlet of the ultrafiltration unit 100.

[0054] In this embodiment, produced water from offshore heavy oil thermal recovery enters the pretreatment device 730 from the raw water tank 710 through the pretreatment pump 720, wherein the pretreatment device 730 is preferably a high-temperature oil removal / suspended matter removal device, and the outlet of the pretreatment device 730 is connected to the inlet of the pretreatment produced water tank 740, so that the produced water after oil removal and suspended matter removal can be stored in the pretreatment produced water tank 740. At the same time, the outlet of the pretreatment produced water tank 740 is connected to the inlet of the ultrafiltration lift pump 110, so that the pretreated produced water can enter the ultrafiltration unit 100 for ultrafiltration.

[0055] In some of the embodiments, the ultrafiltration unit 100 includes an ultrafiltration boost pump 110, a security filter 120, an ultrafiltration water inlet valve E1, an ultrafiltration device 130, an ultrafiltration water production valve E4 and a back pressure valve which are sequentially connected; the liquid inlet end of the ultrafiltration boost pump 110 is connected to the liquid outlet end of the offshore heavy oil thermal recovery produced water pretreatment unit 700, and the liquid outlet end of the back pressure valve is connected to the liquid inlet end of the reverse osmosis unit 200.

[0056] In this embodiment, the pre-treated produced water from offshore heavy oil thermal recovery passes through the ultrafiltration booster pump 110, the safety filter 120, and the ultrafiltration water inlet valve E1 in sequence to enter the ultrafiltration device 130 for ultrafiltration, and the produced water after ultrafiltration passes through the ultrafiltration water production valve E4 and the back pressure valve into the reverse osmosis unit 200.

[0057] Specifically, the ultrafiltration booster pump 110 is provided to provide sufficient pressure for the pre-treated offshore heavy oil thermal recovery water, so that it can smoothly enter the subsequent ultrafiltration device 130 for filtration. At the same time, a security filter 120 is also provided to remove impurities such as tiny particles and suspended matter that may exist in the water, and prevent large particles from entering the ultrafiltration membrane and affecting it, thereby extending the service life of the ultrafiltration membrane.

[0058] Moreover, the liquid inlet and liquid outlet ends of the ultrafiltration device 130 of this embodiment are respectively provided with an ultrafiltration water inlet valve E1 and an ultrafiltration water production valve E4. By reasonably adjusting the ultrafiltration water inlet valve E1 and the ultrafiltration water production valve E4, the water inlet and water production during the ultrafiltration process are controlled to ensure stable operation of the system.

[0059] It should be noted that the ultrafiltration membrane in the ultrafiltration device 130 of this embodiment can intercept impurities such as macromolecular organic matter, colloids, bacteria, etc. in the produced water, allowing water and small molecular solutes to pass through, thereby achieving preliminary separation and purification of the produced water. At the same time, a back pressure valve is also installed at the rear end of the ultrafiltration device 130, which can not only ensure that there is enough pressure at the liquid inlet end of the variable frequency high pressure pump 500 so that the variable frequency high pressure pump 500 can operate normally, but also prevent the pressure fluctuation of the reverse osmosis unit 200 from having a reverse effect on the ultrafiltration unit 100, thereby stabilizing the system pressure. The back pressure valve also has the function of preventing water from flowing back. When the ultrafiltration set A stops running, the back pressure valve can prevent the water produced by other ultrafiltrations from flowing back to the ultrafiltration set A.

[0060] In some of the embodiments, the ultrafiltration unit 100 further includes an upper row valve E3, a lower row valve E2 and an air intake valve E6; the inlet of the upper row valve E3 is connected to the upper row port of the ultrafiltration device 130, the inlet of the lower row valve E2 is connected to the lower row port of the ultrafiltration device 130, and the outlets of the upper row valve E3 and the lower row valve E2 are both used to connect to the ditch; the inlet of the air intake valve E6 is used to input ultrafiltration intake air, and the outlet of the air intake valve E6 is connected to the air intake port of the ultrafiltration device 130.

[0061] In this embodiment, in order to realize the air washing, upper backwashing and lower backwashing of the ultrafiltration device 130, an air inlet valve E6, an upper discharge valve E3 and a lower discharge valve E2 are respectively provided on the external pipeline of the ultrafiltration device 130. Among them, the inlet of the air inlet valve E6 is connected to the external ultrafiltration air inlet, and the outlet of the air inlet valve E6 is connected to the air inlet at the bottom of the ultrafiltration device 130. An upper discharge port is provided at the upper part of the ultrafiltration device 130, one end of the upper discharge valve E3 is connected to the upper discharge port, and the other end is connected to the ditch. A lower discharge port is also provided at the bottom of the ultrafiltration device 130, one end of the lower discharge valve E2 is connected to the lower discharge port, and the other end is also connected to the ditch.

[0062] Specifically, the backwashing sequence of the ultrafiltration device 130 is:

[0063] Ultrafiltration air washing: open the upper discharge valve E3 and the air inlet valve E6 in sequence;

[0064] Ultrafiltration backwash: close the air inlet valve E6 in sequence, open the backwash water inlet valve E5, and the ultrafiltration backwash pump 620;

[0065] Ultrafiltration backwash: open the lower valve E2 and close the upper valve E3 in sequence;

[0066] Ultrafiltration forward wash: turn off the ultrafiltration backwash pump 620 in sequence, open the upper discharge valve E3, close the backwash water inlet valve E5, close the lower discharge valve E2, open the ultrafiltration water inlet valve E1, and turn on the ultrafiltration booster pump 110;

[0067] After flushing is completed, the ultrafiltration booster pump 110 is turned off in sequence, the ultrafiltration water inlet valve E1 is turned off, and the upper discharge valve E3 is turned off.

[0068] It should be noted that the ultrafiltration air intake is preferably compressed air, and the air washing can remove the highly sticky pollutants on the ultrafiltration membrane, so that they can be peeled off from the membrane, reducing the damage to the ultrafiltration membrane. At the same time, by setting the upper discharge valve E3 and the lower discharge valve E2 and controlling their corresponding opening and closing, the upper backwash, lower wash and forward wash of the ultrafiltration device 130 can be realized, and the ultrafiltration device 130 can be cleaned comprehensively and effectively to restore its performance, so as to ensure that the ultrafiltration unit 100 can operate continuously and stably, and provide high-quality influent water for subsequent treatment processes.

[0069] In some of the embodiments, an ultrafiltration backwash unit 600 is also included; the ultrafiltration backwash unit 600 includes a water replenishment valve E9, a backwash water tank 610, a backwash pump 620, an ultrafiltration backwash filter 630 and a backwash inlet valve E5 which are connected in sequence; the water replenishment valve E9 is arranged between the liquid outlet end of the ultrafiltration unit 100 and the liquid inlet end of the backwash water tank 610; the backwash inlet valve E5 is arranged between the liquid outlet end of the ultrafiltration backwash filter 630 and the backwash inlet end of the ultrafiltration unit 100.

[0070] In this embodiment, in order to solve the membrane contamination problem of the ultrafiltration unit 100 and ensure the filtering effect of the ultrafiltration membrane, an ultrafiltration backwash unit 600 is set to backwash the ultrafiltration unit 100 with the self-produced water. Specifically, the liquid outlet of the ultrafiltration unit 100 is connected to the liquid inlet of the water replenishment valve E9. After the ultrafiltration, the produced water flows through the water replenishment valve E9 and enters the backwash water tank 610 for storage. When the system needs to switch to the ultrafiltration backwash state, it flows through the backwash pump 620, the ultrafiltration backwash filter 630 and the backwash water inlet valve E5 in sequence to enter the backwash liquid inlet end of the ultrafiltration unit 100, which is also the liquid inlet end of the reverse osmosis unit 200, to backwash the ultrafiltration membrane to prevent the overall performance of the membrane assembly from decreasing.

[0071] In some of the embodiments, the reverse osmosis unit 200 includes a reverse osmosis device and a reverse osmosis water production valve E11; the liquid inlet end of the reverse osmosis device is connected to the liquid outlet end of the ultrafiltration unit 100, the water production outlet end of the reverse osmosis device is connected to the liquid inlet end of the reverse osmosis water production valve E11, and the liquid outlet end of the reverse osmosis water production valve E11 is used to flow out the clear liquid produced by the reverse osmosis device; the reverse osmosis device is connected to the first water production tank 400 through a pipeline, and a self-cleaning water inlet valve E14 is provided on the pipeline; the number of reverse osmosis devices is less than the number of ultrafiltration devices 130, and the number of ultrafiltration devices 130 is at least two sets.

[0072] In this embodiment, the inlet end of the reverse osmosis device flows into the produced water after being treated by the ultrafiltration unit 100, and the clear liquid after being treated by the reverse osmosis device flows through the reverse osmosis produced water valve E11, and then is reused to the external boiler system or other reuse system. At the same time, in this embodiment, the reverse osmosis device and the first produced water tank 400 are connected by a pipeline, and a self-cleaning water inlet valve E14 is provided on the pipeline. It should be noted that the bottom of the first produced water tank 400 is preferably located at least one meter above the top of the reverse osmosis device. Under this height difference, the clear liquid produced water of the reverse osmosis device can enter the first produced water tank 400 along the pipeline between the reverse osmosis device and the first produced water tank 400, and when self-cleaning is required, it naturally flows back to the clear liquid side of the reverse osmosis device along the same pipeline under the action of gravity.

[0073] In addition, in this embodiment, a self-cleaning water inlet valve E14 is provided on the cleaning pipeline between the first water production tank 400 and the reverse osmosis device. In actual application, the direction of the clear liquid produced by the reverse osmosis device is flexibly controlled by controlling the opening and closing of the self-cleaning water inlet valve E14.

[0074] It should be noted that when the operation state is the reverse osmosis self-cleaning state, the self-cleaning water inlet valve E14 is opened, and the clear liquid in the first water production tank 400 flows back to the reverse osmosis device along the pipeline. At this time, not only can reverse osmosis clear liquid be provided for reverse osmosis membrane cleaning, but the clear liquid flowing back to the reverse osmosis unit 200 under the action of gravity can also generate stable pressure. Compared with the use of other external power sources, such as a booster pump, it can avoid the situation of unstable pressure caused by fluctuations in water pump performance, and ensure that the reverse osmosis membrane can achieve a good cleaning effect.

[0075] It should also be noted that, in the present embodiment, only one pipe is provided between the first water production tank 400 and the reverse osmosis device, and there is no need to provide a plurality of pipes corresponding to the outflow of the clear liquid from the reverse osmosis device and the reflux of the clear liquid in the first water production tank 400. The number of pipes provided between the first water production tank 400 and the reverse osmosis device is reduced while the number of booster pumps provided is reduced, thereby making the overall composition of the system simpler, effectively reducing costs, and reducing system downtime caused by pump failure.

[0076] Furthermore, in this embodiment, a liquid level detection device is preferably provided on the first water production tank 400, and the liquid level of the first water production tank 400 is detected in real time by a liquid level sensor. When there is a self-cleaning demand and the set self-cleaning start liquid level is reached, the self-cleaning water inlet valve E14 is automatically opened, and the valve opening is dynamically adjusted according to the liquid level changes during the cleaning process in combination with the intelligent control system to maintain a stable cleaning pressure and flow, thereby improving the cleaning effect.

[0077] Furthermore, in order to ensure the stable operation of the entire system, avoid frequent start-up or suspension, and reduce the number of flushing times, the number of reverse osmosis devices is preferably set to be less than the number of ultrafiltration devices 130, wherein at least two sets of ultrafiltration devices 130 are preferably set in series. Under the same water inlet conditions, at least two sets of ultrafiltration devices 130 can better share the processing tasks, so that the water quality entering the reverse osmosis device is more stable, and each set of ultrafiltration devices 130 can play a role in removing impurities in the produced water, reducing water quality fluctuations caused by excessive processing load of a single set of ultrafiltration devices 130.

[0078] At the same time, it is more preferred to set at least three sets of ultrafiltration devices 130, of which at least two sets of ultrafiltration devices 130 are in operation and one set of ultrafiltration devices 130 is in standby. When one set of ultrafiltration devices 130 needs to be backwashed or cleaned or fails, at least two other sets of ultrafiltration devices 130 can still work normally. This redundant design greatly enhances the reliability of the system. That is, during the failure or cleaning of a single set of ultrafiltration devices 130, the system will not stop running completely, reducing the possibility of the entire system shutting down due to the failure or cleaning of the ultrafiltration device 130, and ensuring the continuous operation of the system. At the same time, at least one reverse osmosis device is set for every three sets of ultrafiltration devices 130. After the influent is treated by multiple sets of ultrafiltration devices 130, the water quality can reach the influent standard of the reverse osmosis device. Therefore, one set of reverse osmosis device can cope with the produced water after ultrafiltration, realize further fine filtration and desalination, etc., and effectively reduce the investment in operation and maintenance costs.

[0079] The following will take the system setting of three sets of ultrafiltration, ABC, as an example for detailed explanation.

[0080] When the system state is switched from AB set ultrafiltration operation to BC set ultrafiltration operation, open C set ultrafiltration water production valve E4 and C set ultrafiltration water inlet valve E1 in sequence, open C set ultrafiltration booster pump 110, and after the ultrafiltration water production is stable, close A set ultrafiltration booster pump 110, close A set ultrafiltration water inlet valve E1, and close A set ultrafiltration water production valve E4.

[0081] It can be seen that in order to ensure continuous operation of the system, when switching from AB ultrafiltration operation to BC ultrafiltration operation, first open C ultrafiltration water production valve E4 and C ultrafiltration water inlet valve E1, so that C ultrafiltration unit 100 intervenes in the system in a short time and starts ultrafiltration treatment, and then closes the relevant valves and pumps of A ultrafiltration, which can effectively avoid water supply interruption caused by sudden stop of A ultrafiltration device 130. This orderly switching method can ensure that the entire system can stably and continuously provide ultrafiltration treated water to the subsequent reverse osmosis unit 200.

[0082] In some of the embodiments, a variable frequency high pressure pump 500 is disposed between the ultrafiltration unit 100 and the reverse osmosis unit 200 , and a RO water inlet valve E8 is also disposed between the variable frequency high pressure pump 500 and the ultrafiltration unit 100 .

[0083] In this embodiment, only a variable frequency high pressure pump 500 and a RO water inlet valve E8 are added between the ultrafiltration unit 100 and the reverse osmosis unit 200, so that the water produced by the ultrafiltration unit 100 can be directly connected to the reverse osmosis unit 200 for processing, without being stored in an intermediate water tank, and without setting other devices such as filters. Among them, the variable frequency high pressure pump 500 can provide sufficient water inlet pressure for the reverse osmosis unit 200, and the variable frequency high pressure pump 500 can flexibly adjust the pressure according to the actual needs of the reverse osmosis unit 200. When the pollution degree is different or the water quality of the inlet water changes, the output pressure can be adjusted by changing the frequency to ensure the stable operation of the reverse osmosis process. At the same time, the RO water inlet valve E8 and the variable frequency high pressure pump 500 work together to better optimize the system performance, that is, the RO water inlet valve E8 can deliver a stable flow to the variable frequency high pressure pump 500 according to the water inlet demand of the system, and then the variable frequency high pressure pump 500 adjusts the output pressure according to the flow provided by the RO water inlet valve E8 and the pressure requirement of the reverse osmosis unit 200, and the system operates more stably under the synergistic effect of the two.

[0084] In some of the embodiments, the brine recycling unit 300 includes a salt return valve E13, a brine tank 310, a brine pump 320, a brine filter 330 and a salt inlet valve E12 which are connected in sequence; the salt return valve E13 is arranged between the brine outlet end of the reverse osmosis unit 200 and the liquid inlet end of the brine tank 310; the salt inlet valve E12 is arranged between the liquid outlet end of the brine filter 330 and the liquid inlet end of the reverse osmosis unit 200.

[0085] In this embodiment, only a salt return valve E13 is provided on the pipeline between the concentrated brine tank 310 and the reverse osmosis device. Because the reverse osmosis concentrated water pipeline is pressurized, the concentrated brine produced by the reverse osmosis device can flow directly into the concentrated brine tank 310 when the salt return valve E13 is opened, and the concentrated water can be collected without adding other additional equipment between the concentrated brine tank 310 and the reverse osmosis device. In addition, the liquid outlet of the concentrated brine tank 310 is connected to the liquid inlet of the brine pump 320, the liquid outlet of the brine pump 320 is connected to the liquid inlet of the concentrated brine filter 330, the liquid inlet of the salt inlet valve E12 is connected to the liquid outlet of the concentrated brine filter 330, and the liquid outlet of the salt inlet valve E12 is connected to the pipeline between the variable frequency high-pressure pump 500 and the reverse osmosis device. It can be seen that the concentrated water flowing out of the reverse osmosis unit 200 flows into the concentrated brine tank 310 for storage through the return valve E13. When the concentrated water needs to flow back to the concentrated water side of the reverse osmosis unit 200, the concentrated water in the concentrated brine tank 310 flows back to the liquid inlet end of the reverse osmosis unit 200, that is, the concentrated water side, through the brine pump 320, the concentrated brine filter 330 and the salt inlet valve E12 in sequence, providing concentrated water for reverse osmosis self-cleaning.

[0086] Specifically, when the operation state is the reverse osmosis self-cleaning state, after opening the salt inlet valve E12, opening the salt return valve E13, opening the self-cleaning water inlet valve E14, the brine pump 320 is turned on. Under the drive of the brine pump 320, the concentrated water in the concentrated brine tank 310 is filtered by the concentrated brine filter 330 and enters the reverse osmosis unit 200. In this embodiment, a separate brine pump 320 is set in the concentrated brine reuse unit 300, so that when the concentrated water flows back, the flow rate and pressure of the brine pump 320 can be adjusted separately according to the actual needs of self-cleaning, such as cleaning time, cleaning intensity, etc. At the same time, since the concentrated water may contain various impurities, such as tiny particles that are not completely intercepted, precipitation generated by the reaction of too high ion concentration of the concentrated liquid, microorganisms and their metabolites, etc., directly entering the reverse osmosis unit 200 will damage the reverse osmosis membrane. Therefore, in this embodiment, the water outlet of the brine pump 320 is connected to the concentrated brine filter 330, so that the concentrated water can filter out the above impurities after passing through the concentrated brine filter 330, thereby protecting the reverse osmosis unit 200.

[0087] Moreover, the liquid outlet of the salt inlet valve E12 of this embodiment is connected to the pipeline between the variable frequency high pressure pump 500 and the reverse osmosis device, and the concentrated water does not need to pass through the aforementioned processing devices, such as the ultrafiltration unit 100, the variable frequency high pressure pump 500, etc., during the overall process of the concentrated water reflux, which can reduce the risk of impurities mixed into the pipeline. At the same time, the concentrated water reflux path of this embodiment is relatively independent, from the concentrated brine tank 310 to the brine pump 320, to the concentrated brine filter 330, and then to the salt inlet valve E12. The overall connection relationship is clear, and the position of the fault point can be quickly located when the self-cleaning effect is not good or the pipeline is blocked, thereby reducing the difficulty of system maintenance.

[0088] In addition, the concentrated brine tank 310 of the present embodiment is also provided with a liquid level detection device, which cooperates with the corresponding liquid level detection device provided in the first water production tank 400. When it is detected that both the first water production tank 400 and the concentrated brine tank 310 are in a full water state and can meet the use requirements of reverse osmosis self-cleaning, self-cleaning can be started.

[0089] It should also be noted that, in this embodiment, by sequentially connecting the return valve E13, the concentrated brine tank 310, the brine pump 320, the brine filter and the salt inlet valve E12, not only can the recycled concentrated water be realized, but also the return amount of concentrated water can be reasonably controlled by adjusting the opening of the salt inlet valve E12, so that the osmotic pressure on both sides of the membrane can be within a range that is conducive to the self-cleaning process, that is, according to the specific characteristics of the produced water from offshore heavy oil thermal recovery, the position of the first produced water tank 400 and the opening of the salt inlet valve E12 are set in a targeted manner to ensure that the dirt on the membrane surface can be fully flushed under appropriate osmotic pressure, so that the reverse osmosis unit 200 can operate more smoothly.

[0090] In some of the embodiments, a second water production tank 800, a concentrate valve and a concentrate discharge valve E10 are further included; the water inlet end of the second water production tank 800 is connected to the liquid outlet end of the reverse osmosis water production valve E11, and the water outlet end of the second water production tank 800 is used to connect to an external reuse system; the liquid inlet end of the concentrate valve is connected to the concentrate outlet end of the reverse osmosis unit 200, and the liquid outlet end of the concentrate valve is used to connect to an external treatment device; the liquid inlet end of the concentrate discharge valve E10 is connected to the concentrate outlet end of the reverse osmosis unit 200, and the liquid outlet end of the concentrate discharge valve E10 is used to connect to a ditch.

[0091] In this embodiment, a second water production tank 800 is also included. When the system is operating normally, part of the clear liquid of the reverse osmosis unit 200 flows into the second water production tank 800 through the reverse osmosis water production valve E11 for storage to supply the boiler system or other reuse systems. Among them, the first water production tank 400 can cooperate with the second water production tank 800, making the system more flexible in water resource allocation and better adapting to water demand under different working conditions. In addition, if one of the water production tanks needs maintenance, the other water production tank can be used to maintain the supply of recycled water, thereby improving system reliability.

[0092] In addition, an overflow pipe is provided between the second water production tank 800 and the first water production tank 400 in this embodiment, respectively connecting the reused water outlet of the first water production tank 400 and the water inlet of the second water production tank 800. That is, the reused water stored in the first water production tank 400 can also enter the second water production tank 800 through the overflow pipe, and is uniformly sent to the external reuse system by the second water production tank 800. It can be seen from this that when the external reuse system fails, since there is physical isolation between the external reuse system and the reverse osmosis unit 200, changes in external parameters will not affect the reverse osmosis unit 200, nor will they affect the first water production tank 400.

[0093] At the same time, a concentrated water valve and a concentrated water discharge valve E10 are also provided on the corresponding pipeline outside the reverse osmosis unit 200. The liquid inlet end of the concentrated water valve and the concentrated water discharge valve E10 is connected to the concentrated water outlet end of the reverse osmosis unit 200. The liquid outlet end of the concentrated water valve is connected to an external processing device, such as an evaporation device or any device that needs to use concentrated water, and the liquid outlet end of the concentrated water discharge valve E10 is connected to a ditch. When the system is operating normally, part of the concentrated water flows into other external devices that need concentrated water through the concentrated water valve for use, or flows into the evaporation device for evaporation, and part of the concentrated water flows into the concentrated brine tank 310 through the salt return valve E13; when the system state is the reverse osmosis self-cleaning state, the concentrated water in the concentrated brine tank 310 flows back to the concentrated water side of the reverse osmosis unit 200, and acts together with the clear liquid returned from the first water production tank 400 to clean the reverse osmosis membrane, and the cleaning waste liquid after self-cleaning flows out from the concentrated water discharge valve E10. It can be seen that this embodiment can flexibly control the direction of the concentrate of the reverse osmosis unit 200 by correspondingly arranging the concentrate valve, the concentrate discharge valve E10 and the salt return valve E13 on the outside of the concentrate outlet of the reverse osmosis unit 200, so as to cope with different working conditions and needs, and can effectively guarantee normal production, equipment maintenance and subsequent recovery operation.

[0094] The following is a detailed description of the water pump and valve sequence control of the offshore heavy oil thermal recovery produced water deep treatment and reuse system of the present application.

[0095] 1. Start operation after overall shutdown:

[0096] (1) Flushing ultrafiltration: Open the ultrafiltration upper discharge valve E3, the ultrafiltration water inlet valve E1, and the ultrafiltration booster pump 110 in sequence, and run for 30-60 seconds;

[0097] (2) Adjust to flushing reverse osmosis: open the reverse osmosis RO water inlet valve E8, the reverse osmosis concentrated water discharge valve E10 and the reverse osmosis water production valve E11 at the same time; open the ultrafiltration water production valve E4 and close the ultrafiltration upper discharge valve E3 in turn, and the operation time is 60-120s;

[0098] (3) Adjust to the operating state: close the reverse osmosis concentrated water discharge valve E10 in sequence, start the reverse osmosis variable frequency high-pressure pump 500, and run it for 5-24 hours.

[0099] 2. Reverse osmosis self-cleaning:

[0100] (1) The operation state is adjusted to the reverse osmosis self-cleaning state: turn off the ultrafiltration boost pump 110 and the reverse osmosis variable frequency high-pressure pump 500, then turn off the ultrafiltration water production valve E4, turn off the ultrafiltration water inlet valve E1, turn off the RO water inlet valve E8, open the salt inlet valve E12, open the salt return valve E13, open the self-cleaning water inlet valve E14, and finally turn on the brine pump 320;

[0101] (2) The self-cleaning operation time is 5-15 minutes. The osmotic pressure on both sides of the membrane and the pressure difference of the high-level first water production tank 400 are used to make the produced water pass through the membrane surface to the concentrated water side, flushing away the pollutants in the membrane pores and dispersing the bacterial clusters in the dead corners of the concentrated water side;

[0102] (3) Adjust to reverse osmosis flushing state: turn off the brine pump 320, and turn off the salt inlet valve E12 and the salt return valve E13 in sequence, turn off the self-cleaning water inlet valve E14, open the RO water inlet valve E8 and the ultrafiltration water production valve E4, open the ultrafiltration water inlet valve E1, and finally turn on the ultrafiltration booster pump 110. When the conductivity index of the concentrated water side is close to that of the inlet water, the flushing is completed, and the operation time is 60-180s;

[0103] (4) Adjust to the operating state: close the reverse osmosis concentrated water discharge valve E10 in sequence, start the reverse osmosis variable frequency high pressure pump 500, and run it for 5-24 hours.

[0104] 3. Ultrafiltration set switching:

[0105] (1) The operation state is adjusted to the reverse osmosis flushing state: the reverse osmosis concentrated water discharge valve E10 is opened in sequence, and the reverse osmosis variable frequency high-pressure pump 500 is closed, and the operation time is 60-120s;

[0106] (2) Switch the AB set ultrafiltration operation to the BC set ultrafiltration operation: Open the C set ultrafiltration water production valve E4, open the C set ultrafiltration water inlet valve E1, and open the C set ultrafiltration booster pump 110 in sequence. After the ultrafiltration water production is stable, close the A set ultrafiltration booster pump 110, close the A set ultrafiltration water inlet valve E1, and close the A set ultrafiltration water production valve E4.

[0107] (3) Adjust to the operating state: close the reverse osmosis concentrated water discharge valve E10 in sequence, and start the reverse osmosis variable frequency high-pressure pump 500.

[0108] 4. Overall shutdown:

[0109] (1) Reverse osmosis flushing: Open the reverse osmosis concentrated water discharge valve E10 and close the reverse osmosis variable frequency high-pressure pump 500 in sequence, and run for 60-120 seconds;

[0110] (2) Shutdown: turn off the ultrafiltration boost pump 110, the ultrafiltration water inlet valve E1, the ultrafiltration water production valve E4, the reverse osmosis RO water inlet valve E8, the reverse osmosis water production valve E11, and the reverse osmosis concentrated water valve in sequence.

[0111] In a second aspect, an embodiment of the present application provides a method for deep treatment and reuse of produced water from thermal recovery of offshore heavy oil, which is implemented by using any of the above-mentioned systems for deep treatment and reuse of produced water from thermal recovery of offshore heavy oil, and includes the following steps:

[0112] The pre-treated produced water from thermal recovery of offshore heavy oil is subjected to ultrafiltration treatment to obtain ultrafiltration produced water;

[0113] After the ultrafiltration water is subjected to reverse osmosis treatment, clear liquid and concentrated water are obtained respectively; among them, a part of the clear liquid is recycled to the external recycling system, and the other part of the clear liquid is stored in the high-position first water production tank 400, so as to be returned to the clear water side of the membrane during self-cleaning of the reverse osmosis membrane, and cooperate with the concentrated water returned to the concentrated water side of the membrane to clean the membrane.

[0114] In this embodiment, the pretreated produced water from offshore heavy oil thermal recovery is specifically the produced water obtained after the raw water of offshore heavy oil thermal recovery passes through the pretreatment pump 720 to the high-temperature oil removal and high-temperature suspended solids removal device for treatment. In the water treatment process, the pretreated produced water is sequentially sent to the ultrafiltration unit 100 through the ultrafiltration lift pump 720 and the security filter 120 for ultrafiltration treatment, and the clear liquid after ultrafiltration, i.e., ultrafiltration produced water, is obtained under the action of the ultrafiltration membrane. It should be noted that in this embodiment, a part of the ultrafiltration produced water is further reverse osmosis treated in the reverse osmosis unit 200 through the variable frequency high-pressure pump 500, and the other part of the ultrafiltration produced water flows into the ultrafiltration backwash water tank 610 for storage, so that when the ultrafiltration membrane is cleaned, the ultrafiltration produced water can be sequentially refluxed to the ultrafiltration device 130 through the backwash pump 620 and the ultrafiltration backwash filter 630 to clean the ultrafiltration membrane to ensure the treatment effect of the ultrafiltration membrane.

[0115] Furthermore, when the ultrafiltration produced water is subjected to reverse osmosis treatment, the ultrafiltration produced water enters the reverse osmosis device for desalination in sequence through the ultrafiltration produced water valve E4, the back pressure valve, the RO water inlet valve E8 and the variable frequency high pressure pump 500, and the reverse osmosis clear liquid and the reverse osmosis concentrated liquid, i.e., clear liquid and concentrated water, are obtained respectively. Among them, a part of the clear liquid flows into the first produced water tank 400 through the self-cleaning water inlet valve E14 for storage, so as to be used for reverse osmosis self-cleaning and reused to the external boiler system or other reuse systems, and a part of the clear liquid flows into the second produced water tank 800 through the reverse osmosis produced water valve E11 for reuse to the external boiler system or other reuse systems; the concentrated water enters the concentrated brine tank 310 for storage through the salt return valve E13, so as to be returned to the concentrated water side of the reverse osmosis device during reverse osmosis self-cleaning. It can be seen that the method of this embodiment is implemented by directly sending the ultrafiltration water into the reverse osmosis device for desalination, without intermediate residence time, which can reduce the occurrence of flocculation after the ultrafiltration unit 100, thereby reducing the probability of reverse osmosis fouling, allowing the reverse osmosis device to operate normally, and realizing the treatment of produced water from offshore heavy oil thermal recovery.

[0116] Among them, when the operation is started after the overall shutdown, the ultrafiltration upper discharge valve E3, the ultrafiltration water inlet valve E1 and the ultrafiltration booster pump 110 arranged outside the ultrafiltration device 130 are opened in sequence to flush the ultrafiltration, and the specific operation time is 30s-60s; when the reverse osmosis water inlet valve E8, the reverse osmosis concentrated water discharge valve E10 and the reverse osmosis water production valve E1 are opened at the same time, and the ultrafiltration water production valve E4 is opened in sequence and the ultrafiltration upper discharge valve E3 is closed, the operation state is adjusted to flushing the reverse osmosis, and the specific operation time is 60s-120s; by closing the reverse osmosis concentrated water discharge valve E10 in sequence, turning on the variable frequency high-pressure pump 500 to adjust to the operation state, the specific operation time is 5-24h, that is, under the action of the variable frequency high-pressure pump 500, the ultrafiltration water can enter the reverse osmosis device for desalination, thereby obtaining a reverse osmosis clear liquid that can be reused in an external boiler system or other reuse systems. If the entire system needs to be shut down, the reverse osmosis concentrate discharge valve E10 is opened in sequence, and the reverse osmosis variable frequency high-pressure pump 500 is closed for reverse osmosis flushing, with a running time of 60-120 seconds. Subsequently, the ultrafiltration booster pump 110, the ultrafiltration water inlet valve E1, the ultrafiltration water production valve E4, the RO water inlet valve E8, the reverse osmosis water production valve E11 and the reverse osmosis concentrate valve are closed in sequence to achieve the shutdown purpose.

[0117] It should be noted that in order to ensure the reverse osmosis treatment effect, the present embodiment uses reverse osmosis self-produced water to clean the reverse osmosis membrane inside it, and returns the concentrated brine inside the concentrated brine tank 310 to the reverse osmosis concentrated water side, and returns the clear liquid in the high-level water production tank to the reverse osmosis clear water side, so that the osmotic pressure on both sides of the membrane and the pressure difference of the high-level water production tank can be used to make the clear liquid pass through the membrane surface to the concentrated water side, flushing away the pollutants in the membrane pores and the bacterial clusters in the dead corners of the concentrated water side, thereby ensuring the normal function of the reverse osmosis membrane, so that the produced water after ultrafiltration can be further desalinated.

[0118] Among them, during the reverse osmosis self-cleaning, the operation state needs to be adjusted to the reverse osmosis self-cleaning state first, specifically including closing the ultrafiltration booster pump 110 and the reverse osmosis variable frequency high-pressure pump 500, and then closing the ultrafiltration water production valve E4, closing the ultrafiltration water inlet valve E1, closing the RO water inlet valve E8, opening the salt inlet valve E12, opening the salt return valve E13, opening the self-cleaning water production valve E14, and finally opening the brine pump 320, and self-cleaning operation for 5-15 minutes. And when the operation state is adjusted to the reverse osmosis flushing state after the cleaning is completed, the brine pump 320 is closed in sequence, the salt inlet valve E12 and the salt return valve E13 are opened, and the self-cleaning water inlet valve E14 is closed in sequence, the RO water inlet valve E8 and the ultrafiltration water production valve E4 are opened, the ultrafiltration water inlet valve E1 is opened, and finally the ultrafiltration booster pump 110 is opened. The flushing is completed after the conductivity index of the concentrated water side is close to that of the inlet water, and the operation time is 60-180s. Then, the reverse osmosis concentrated water discharge valve E10 is closed in sequence, and the reverse osmosis variable frequency high pressure pump 500 is turned on and operated for 5-24 hours. It can be seen that the time from switching to the reverse osmosis self-cleaning state to switching back to the normal operating state in this embodiment can be controlled within 18 minutes, which greatly shortens the cleaning time of the reverse osmosis membrane.

[0119] The above embodiments only express several implementation methods of the present application, and the descriptions thereof are relatively specific and detailed, but the limitation of the scope of the invention patent cannot be understood as a result. It should be pointed out that, for a person of ordinary skill in the art, several modifications or improvements can be made without departing from the concept of the present application, and these all belong to the protection scope of the present application. Therefore, the protection scope of the patent of the present application shall be subject to the attached claims.

Claims

1. A system for deep treatment and reuse of produced water from offshore heavy oil thermal recovery, characterized in that: It includes an ultrafiltration unit, a reverse osmosis unit, a concentrated brine recycling unit and a first water production tank; The liquid inlet of the ultrafiltration unit is used to communicate with the liquid outlet of the offshore heavy oil thermal recovery produced water pretreatment unit, and the liquid outlet of the ultrafiltration unit is communicated with the liquid inlet of the reverse osmosis unit; The water outlet of the reverse osmosis unit is connected to the water inlet of the first water production tank, and the water outlet of the first water production tank is used to communicate with an external recycling system; and the bottom of the first water production tank is arranged higher than the top of the reverse osmosis unit, and the clear liquid in the first water production tank can flow back to the reverse osmosis unit; The concentrated water outlet of the reverse osmosis unit is communicated with the liquid inlet of the concentrated brine recycling unit, and the liquid outlet of the concentrated brine recycling unit is communicated with the liquid inlet of the reverse osmosis unit.

2. The system for deep treatment and reuse of produced water from offshore heavy oil thermal recovery according to claim 1, characterized in that: Also includes a pre-processing unit; The pretreatment unit comprises a raw water tank, a pretreatment pump, a pretreatment device and a pretreatment water production tank which are connected in sequence; The liquid outlet of the pre-treatment water production tank is communicated with the liquid inlet of the ultrafiltration unit.

3. The system for deep treatment and reuse of produced water from offshore heavy oil thermal recovery according to claim 1, characterized in that: The ultrafiltration unit comprises an ultrafiltration lift pump, a safety filter, an ultrafiltration water inlet valve, an ultrafiltration device, an ultrafiltration water production valve and a back pressure valve which are connected in sequence; The liquid inlet end of the ultrafiltration lift pump is communicated with the liquid outlet end of the offshore heavy oil thermal recovery produced water pretreatment unit, and the liquid outlet end of the back pressure valve is communicated with the liquid inlet end of the reverse osmosis unit.

4. The system for deep treatment and reuse of produced water from offshore heavy oil thermal recovery according to claim 3, characterized in that: The ultrafiltration unit also includes an upper row valve, a lower row valve and an air inlet valve; The inlet of the upper row valve is communicated with the upper row port of the ultrafiltration device, the inlet of the lower row valve is communicated with the lower row port of the ultrafiltration device, and the outlets of the upper row valve and the lower row valve are both used to communicate with the ditch; The inlet of the air intake valve is used to input ultrafiltration air intake, and the outlet of the air intake valve is communicated with the air intake of the ultrafiltration device.

5. The system for deep treatment and reuse of produced water from offshore heavy oil thermal recovery according to claim 1, characterized in that: It also includes an ultrafiltration backwash unit; The ultrafiltration backwash unit comprises a water replenishment valve, a backwash water tank, a backwash pump, an ultrafiltration backwash filter and a backwash water inlet valve which are connected in sequence; The water supply valve is arranged between the liquid outlet of the ultrafiltration unit and the liquid inlet of the backwash water tank; The backwash water inlet valve is arranged between the liquid outlet end of the ultrafiltration backwash filter and the backwash liquid inlet end of the ultrafiltration unit.

6. The system for deep treatment and reuse of produced water from offshore heavy oil thermal recovery according to claim 3, characterized in that: The reverse osmosis unit includes a reverse osmosis device and a reverse osmosis water production valve; The liquid inlet of the reverse osmosis device is connected to the liquid outlet of the ultrafiltration unit, the water outlet of the reverse osmosis device is connected to the liquid inlet of the reverse osmosis water production valve, and the liquid outlet of the reverse osmosis water production valve is used to flow out the clear liquid produced by the reverse osmosis device; The reverse osmosis device is connected to the first water production tank through a pipeline, and a self-cleaning water inlet valve is provided on the pipeline; The number of the reverse osmosis devices is less than the number of the ultrafiltration devices, and the number of the ultrafiltration devices is at least two sets.

7. The system for deep treatment and reuse of produced water from offshore heavy oil thermal recovery according to claim 1, characterized in that: A variable frequency high pressure pump is arranged between the ultrafiltration unit and the reverse osmosis unit, and an RO water inlet valve is also arranged between the variable frequency high pressure pump and the ultrafiltration unit.

8. The system for deep treatment and reuse of produced water from offshore heavy oil thermal recovery according to claim 1, characterized in that: The concentrated brine recycling unit comprises a salt return valve, a concentrated brine tank, a brine pump, a concentrated brine filter and a salt inlet valve which are sequentially connected; The salt return valve is arranged between the concentrated water outlet of the reverse osmosis unit and the concentrated water inlet of the concentrated brine tank; The salt inlet valve is arranged between the liquid outlet end of the concentrated salt water filter and the liquid inlet end of the reverse osmosis unit.

9. The system for deep treatment and reuse of produced water from offshore heavy oil thermal recovery according to claim 6, characterized in that: It also includes a second water production tank, a concentrate valve and a concentrate discharge valve; The water inlet end of the second water production tank is connected to the liquid outlet end of the reverse osmosis water production valve, and the water outlet end of the second water production tank is used to communicate with an external reuse system; The liquid inlet end of the concentrated water valve is connected to the concentrated water outlet end of the reverse osmosis unit, and the liquid outlet end of the concentrated water valve is used to connect to an external processing device; The liquid inlet end of the concentrated water discharge valve is communicated with the concentrated water outlet end of the reverse osmosis unit, and the liquid outlet end of the concentrated water discharge valve is used to communicate with the ditch.

10. A method for deep treatment and reuse of produced water from thermal recovery of offshore heavy oil, which is implemented by using the system for deep treatment and reuse of produced water from thermal recovery of offshore heavy oil according to any one of claims 1 to 9, characterized in that: The steps include: The pre-treated produced water from thermal recovery of offshore heavy oil is subjected to ultrafiltration treatment to obtain ultrafiltration produced water; After the ultrafiltration water is subjected to reverse osmosis treatment, a clear liquid and concentrated water are obtained respectively; among which, a part of the clear liquid is recycled to the external recycling system, and the other part of the clear liquid is stored in the high-position first water production tank to be returned to the clear water side of the membrane during self-cleaning of the reverse osmosis membrane, and cooperated with the concentrated water returned to the concentrated water side of the membrane to clean the membrane.

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