FPSO reinjection water preparation system and method

Abstract

The invention belongs to the technical field of water treatment, and particularly relates to a preparation system and method of FPSO reinjection water. In the preparation system disclosed by the invention, the ultrafiltration device (the used filter membrane is a horizontal ultrafiltration membrane with high pressure bearing capacity) is specially arranged, and the flow and pressure of the ultrafiltration device are adjusted, so that the effluent of the ultrafiltration device is the effluent with the pressure of 0.2 MPa, and the effluent with the pressure can directly enter the deoxidization device for deoxidization by utilizing the pressure of the effluent with the pressure; and use of a middle water tank and a middle booster pump is avoided. Meanwhile, the deoxidation device is arranged between the ultrafiltration device and the nanofiltration device, so that the risk that sulfate exceeds the standard is reduced, a reducing agent adding device and a reinjection water tank are omitted, and the occupied area, the energy consumption and the cost are optimized.

Description

Technical Field

[0001] The present invention relates to the technical field of water treatment, and in particular to a system and method for preparing FPSO reinjection water. Background Art

[0002] The reinjection water of FPSO (Floating Liquefied Natural Gas Production, Storage and Offloading) is a key link in maintaining efficient oil field development and environmentally friendly production. Its core function is to reinject qualified treated water into the oil reservoir to maintain formation pressure and increase crude oil recovery.

[0003] Existing methods for removing sulfate from seawater for reinjection water typically involve passing seawater through a water intake pump, a first dosing device (for adding flocculants, coagulants, and biocides), a settling tank, a coarse filter, an ultrafiltration device, an intermediate water tank, a seawater degassing device, an intermediate booster pump, a precision filter, a second dosing device (for adding scale inhibitors and reducing agents), a high-pressure pump, a nanofiltration device, a deoxygenator, and a reinjection water tank. The disadvantages of this prior art are the cumbersome process flow. The settling tank, intermediate water tank, intermediate booster pump, second dosing device, and reinjection water tank increase the total footprint of the device, increase energy consumption, and raise treatment costs. Furthermore, the deoxygenator, placed after the nanofiltration process, poses a risk of excessive sulfate levels. Summary of the Invention

[0004] In light of this, the present invention aims to provide a system and method for preparing FPSO reinjection water. This system omits an intermediate water tank, intermediate booster pump, reducing agent dosing device, and reinjection water tank, thereby optimizing floor space, energy consumption, and costs. Furthermore, the deoxygenation device is positioned between the ultrafiltration and nanofiltration devices, reducing the risk of excessive sulfate levels.

[0005] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0006] The present invention provides a FPSO reinjection water preparation system, comprising a water intake pump 1;

[0007] a coarse filter 3 connected to the water outlet of the water intake pump 1;

[0008] An ultrafiltration device 4 is connected to the water outlet of the coarse filter 3, and a fungicide dosing device 2 is provided on the pipeline connecting the coarse filter 3 and the ultrafiltration device 4;

[0009] a deoxidation device 5 connected to the water outlet of the ultrafiltration device 4;

[0010] a deoxidizer dosing device 6 connected to the deoxidizer 5;

[0011] a safety filter 7 connected to the water outlet of the deoxidation device 5;

[0012] A first booster pump 9 and a second booster pump 12 are respectively connected to the water outlet of the security filter 7; an antiscalant dosing device 8 is provided on the pipeline connecting the security filter 7 and the first booster pump 9 and the second booster pump 12;

[0013] a nanofiltration device 10 connected to the water outlet of the first booster pump 9;

[0014] an RO reverse osmosis device 11 connected to the outlet water of the second booster pump 12;

[0015] The ultrafiltration device 4 includes an ultrafiltration inlet and a flow regulating valve arranged at the ultrafiltration inlet;

[0016] The filter membrane used in the ultrafiltration device 4 is a horizontal ultrafiltration membrane.

[0017] Preferably, the coarse filter 3 is an automatic backwashing filter.

[0018] The present invention also provides a method for preparing FPSO reinjection water using the preparation system described in the above technical solution, comprising the following steps:

[0019] The seawater is extracted by the water pump 1 and enters the coarse filter 3 for coarse filtration to obtain a coarse filtrate;

[0020] A bactericide is added to the coarse filtration through a bactericide dosing device 2 for sterilization to obtain a sterilization system;

[0021] The sterilization system enters the ultrafiltration device 4 for ultrafiltration to obtain pressurized ultrafiltrate;

[0022] The pressurized ultrafiltrate enters the deoxidation device 5, and a deoxidizer is added to the deoxidizer 5 through the deoxidizer dosing device 6 to perform deoxidation to obtain a deoxidized liquid.

[0023] The deoxygenated liquid enters the safety filter 7 for safety filtration to obtain safety filtrate;

[0024] The scale inhibitor is added through the scale inhibitor dosing device 8 and mixed with the security filtrate. The resulting mixed system is split and pressurized by the first booster pump 9 and the second booster pump 12 respectively to obtain the first pressurized water and the second pressurized water respectively.

[0025] The first pressurized water enters the nanofiltration device 10 for nanofiltration to obtain the FPSO reinjection water;

[0026] The second pressurized water enters the RO reverse osmosis device 11 for reverse osmosis to obtain reverse osmosis water.

[0027] Preferably, the bactericide comprises sodium hypochlorite.

[0028] Preferably, the pressure of the pressurized ultrafiltrate is 0.2 MPa.

[0029] Preferably, the deoxidizer comprises bisulfite.

[0030] Preferably, the bisulfite comprises sodium bisulfite.

[0031] Preferably, the bisulfite comprises a first portion of bisulfite and a second portion of bisulfite;

[0032] The molar ratio of the first portion of bisulfite to the hypochlorite in the pressurized ultrafiltrate is 3:1;

[0033] The amount of the second portion of bisulfite added is 0.6 g / h per ton of seawater.

[0034] Preferably, the deoxidation is carried out under spraying conditions, the deoxidation temperature is 18 to 40° C., and the deoxidation time is 2 to 10 minutes.

[0035] Preferably, the sulfate content in the FPSO reinjection water is less than 20 mg / L, and the oxygen content is less than 10 μg / L.

[0036] The invention provides a preparation system for FPSO reinjection water.

[0037] The preparation system of the present invention achieves pressurized water outlet from the ultrafiltration device by regulating the flow rate and pressure before the ultrafiltration device. This pressurized water can directly enter the deoxygenation device for deoxygenation using its own pressure, eliminating the need for an intermediate water tank and intermediate booster pump. Furthermore, the ultrafiltration device uses a horizontal ultrafiltration membrane. Furthermore, the placement of the deoxygenation device between the ultrafiltration device and the nanofiltration device reduces the risk of excessive sulfate levels and eliminates the need for a reducing agent dosing device and a refill water tank, thereby optimizing floor space, energy consumption, and costs.

[0038] The present invention also provides a method for preparing FPSO reinjection water using the preparation system described in the above technical solution. The method of the present invention has a simple process.

[0039] Furthermore, by using bisulfite as a deoxidizer, deep deoxygenation is achieved while also serving as a reducing agent to neutralize and remove the bactericide, eliminating the need for subsequent addition of reducing agents, and thus eliminating the need for a reducing agent dosing device before the nanofiltration device, thereby optimizing floor space, cost, and energy consumption. It also reduces the risk of excessive sulfate levels resulting from subsequent addition of reducing agents, allowing the resulting FPSO reinjection water to meet the requirements of low sulfate and low oxygen. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 Schematic diagram of the FPSO reinjection water preparation system provided by the present invention;

[0041] The figures are marked as follows: 1-water intake pump, 2-bactericide dosing device, 3-coarse filter, 4-ultrafiltration device, 5-deoxygenation device, 6-deoxygenator dosing device, 7-security filter, 8-scaling inhibitor dosing device, 9-first booster pump, 10-nanofiltration device, 11-RO reverse osmosis device, 12-second booster pump. DETAILED DESCRIPTION

[0042] Figure 1 Schematic diagram of the preparation system of FPSO reinjection water provided by the present invention, Figure 1 The preparation system provided by the present invention is described.

[0043] The present invention provides a FPSO reinjection water preparation system, comprising a water intake pump 1;

[0044] a coarse filter 3 connected to the water outlet of the water intake pump 1;

[0045] An ultrafiltration device 4 is connected to the water outlet of the coarse filter 3, and a fungicide dosing device 2 is provided on the pipeline connecting the coarse filter 3 and the ultrafiltration device 4;

[0046] a deoxidation device 5 connected to the water outlet of the ultrafiltration device 4;

[0047] a deoxidizer dosing device 6 connected to the deoxidizer 5;

[0048] a safety filter 7 connected to the water outlet of the deoxidation device 5;

[0049] A first booster pump 9 and a second booster pump 12 are respectively connected to the water outlet of the security filter 7; an antiscalant dosing device 8 is provided on the pipeline connecting the security filter 7 and the first booster pump 9 and the second booster pump 12;

[0050] a nanofiltration device 10 connected to the water outlet of the first booster pump 9;

[0051] an RO reverse osmosis device 11 connected to the outlet water of the second booster pump 12;

[0052] The ultrafiltration device 4 includes an ultrafiltration inlet and a flow regulating valve arranged at the ultrafiltration inlet;

[0053] The filter membrane used in the ultrafiltration device 4 is a horizontal ultrafiltration membrane.

[0054] The FPSO reinjection water preparation system provided by the present invention comprises a water intake pump 1, wherein the water intake pump 1 is used to extract seawater; the depth of the extracted seawater is preferably 100 meters below sea level.

[0055] The FPSO reinjection water preparation system provided by the present invention comprises a coarse filter 3 connected to the water outlet of the water intake pump 1. In the present invention, the coarse filter 3 is preferably an automatic backwashing filter.

[0056] The preparation system for FPSO reinjection water provided by the present invention includes an ultrafiltration device 4 connected to the water outlet of the coarse filter 3. In the present invention, the filter membrane used in the ultrafiltration device 4 is a horizontal ultrafiltration membrane. In the present invention, the ultrafiltration device 4 includes an ultrafiltration inlet and a flow regulating valve arranged at the ultrafiltration inlet. In the present invention, by adjusting the water flow and pressure of the ultrafiltration inlet, the water outlet of the ultrafiltration device is pressurized water, and the horizontal ultrafiltration membrane is used as the filter membrane, which has high pressure resistance and can achieve ultrafiltration of high-pressure water production. In the present invention, the special setting of the ultrafiltration device realizes that the ultrafiltration water outlet is pressurized water, and the pressurized water outlet can directly enter the deoxygenation device for deoxygenation using its own pressure, eliminating the use of the intermediate water tank and the intermediate booster pump, and avoiding the space occupied, investment and energy consumption of the intermediate water tank and the intermediate booster pump. In the present invention, the filter membrane of the ultrafiltration device 4 is preferably a horizontal ultrafiltration membrane. In the present invention, the filter membrane of the ultrafiltration device 4 is a horizontal ultrafiltration membrane, which saves 69% of the floor space compared to the traditional vertical installation.

[0057] In the present invention, a bactericide dosing device 2 is provided on the pipeline connecting the coarse filter 3 and the ultrafiltration device 4. In the present invention, the bactericide dosing device is used to add bactericide.

[0058] The FPSO reinjection water preparation system provided by the present invention comprises a deoxidation device 5 connected to the water outlet of the ultrafiltration device 4. In the present invention, the deoxidation device is used for deoxidation.

[0059] The FPSO reinjection water preparation system provided by the present invention includes a deoxidizer dosing device 6 connected to the deoxidizer 5. In the present invention, the deoxidizer dosing device 6 is used to add deoxidizer. The deoxidizer 5 is positioned between the ultrafiltration device 4 and the nanofiltration device 10. Excess deoxidizer can be removed in the nanofiltration device 10. When the deoxidizer is bisulfite, the risk of excessive sulfate in the FPSO reinjection water is reduced. Furthermore, the installation of a reducing agent dosing device before the nanofiltration device is eliminated, reducing the device's footprint, investment, and energy consumption.

[0060] The FPSO reinjection water preparation system provided by the present invention includes a safety filter 7 connected to the water outlet of the deoxidation device 5 .

[0061] The FPSO reinjection water preparation system provided by the present invention includes a first booster pump 9 and a second booster pump 12 respectively connected to the water outlet of the safety filter 7.

[0062] In the present invention, an antiscalant dosing device 8 is installed on the pipeline connecting the safety filter 7 and the first and second booster pumps 9 and 12. In the present invention, the antiscalant dosing device is preferably installed before the diversion. In the present invention, the antiscalant dosing device is used to add antiscalant.

[0063] The FPSO reinjection water preparation system provided by the present invention comprises a nanofiltration device 10 connected to the water outlet of the first booster pump 9. In the present invention, the nanofiltration device is used for desalination.

[0064] The FPSO reinjection water preparation system provided by the present invention includes an RO reverse osmosis device 11 connected to the water outlet of the second booster pump 12 .

[0065] The present invention also provides a method for preparing FPSO reinjection water using the preparation system described in the above technical solution, comprising the following steps:

[0066] The seawater is extracted by the water pump 1 and enters the coarse filter 3 for coarse filtration to obtain a coarse filtrate;

[0067] A bactericide is added to the coarse filtrate by a bactericide dosing device 2 to sterilize the coarse filtrate, thereby obtaining a sterilization system;

[0068] The sterilization system enters the ultrafiltration device 4 for ultrafiltration to obtain pressurized ultrafiltrate;

[0069] The pressurized ultrafiltrate enters the deoxidation device 5, and a deoxidizer is added to the deoxidizer 5 through the deoxidizer dosing device 6 to perform deoxidation to obtain a deoxidized liquid.

[0070] The deoxygenated liquid enters the safety filter 7 for safety filtration to obtain safety filtrate;

[0071] The scale inhibitor is added through the scale inhibitor dosing device 8 and mixed with the security filtrate. The resulting mixed system is split and pressurized by the first booster pump 9 and the second booster pump 12 respectively to obtain the first pressurized water and the second pressurized water respectively.

[0072] The first pressurized water enters the nanofiltration device 10 for nanofiltration to obtain the FPSO reinjection water.

[0073] The second pressurized water enters the RO reverse osmosis device 11 for reverse osmosis to obtain reverse osmosis water.

[0074] The present invention uses a water pump 1 to extract seawater, and the seawater enters a coarse filter 3 for coarse filtration to obtain a coarse filtrate. In the present invention, the coarse filtration can remove suspended matter, colloid, organic matter, etc., meeting the water inlet requirements of the ultrafiltration device.

[0075] After obtaining the coarse filtrate, the present invention adds a bactericide to the coarse filtrate via a bactericide dosing device 2 to sterilize the coarse filtrate, thereby obtaining a sterilization system. In the present invention, the bactericide preferably comprises sodium hypochlorite. In the present invention, the amount of the bactericide added is preferably excessive. In the present invention, the addition of the bactericide can inhibit bacteria.

[0076] The sterilization system is obtained, and the present invention enters the sterilization system into the ultrafiltration device 4 for ultrafiltration to obtain a pressurized ultrafiltrate. In the present invention, the pressure of the pressurized ultrafiltrate is preferably 0.2 MPa. In the present invention, the ultrafiltration can achieve ultrafiltration while also making the effluent obtained by the ultrafiltration into a pressurized ultrafiltrate; the pressurized ultrafiltrate can directly enter the deoxygenation device for deoxygenation using its own pressure.

[0077] After obtaining the pressurized ultrafiltrate, the pressurized ultrafiltrate of the present invention enters the deoxygenation device 5, and a deoxidizer is added to the deoxygenation device 5 via the deoxidizer dosing device 6 to perform deoxygenation to obtain a deoxygenated liquid. In the present invention, the deoxidizer preferably includes bisulfite. In the present invention, the bisulfite preferably includes sodium bisulfite. In the present invention, the bisulfite preferably includes a first portion of bisulfite and a second portion of bisulfite.

[0078] In the present invention, the molar ratio of the first portion of bisulfite to the hypochlorite in the pressurized ultrafiltrate is preferably 3:1. In the present invention, the amount of hypochlorite in the pressurized ultrafiltrate is preferably measured using a residual chlorine detector. In the present invention, the first portion of bisulfite is used to neutralize the fungicide sodium hypochlorite; neutralization of the fungicide sodium hypochlorite effectively protects the subsequent nanofiltration device and RO reverse osmosis device, and avoids the subsequent addition of a reducing agent.

[0079] In the present invention, the amount of the second portion of bisulfite added is preferably 0.6 g / h per ton of seawater. In the present invention, the second portion of bisulfite is used to remove oxygen from the pressurized ultrafiltrate.

[0080] In the present invention, the deoxidation is preferably carried out under spraying conditions, the deoxidation temperature is preferably 18 to 40° C., and the deoxidation time is preferably 2 to 10 minutes.

[0081] The present invention uses bisulfite as a deoxidizer to achieve deep deoxidation while also serving as a reducing agent to neutralize and remove the bactericide, eliminating the need for subsequent addition of a reducing agent and further eliminating the need for a reducing agent dosing device before a nanofiltration device, thereby optimizing floor space, cost, and energy consumption; and reducing the risk of excessive sulfate levels resulting from subsequent addition of a reducing agent.

[0082] After the deoxygenated liquid is obtained, the deoxygenated liquid of the present invention enters the safety filter 7 for safety filtration to obtain safety filtrate. The present invention does not make any specific limitation on the safety filtration.

[0083] After obtaining the security filtrate, the present invention adds a scale inhibitor via the scale inhibitor dosing device 8 and mixes it with the security filtrate. The resulting mixed system is then split and pressurized by a first booster pump 9 and a second booster pump 12, respectively, to produce first and second pressurized water, respectively. The present invention does not specifically limit the type and amount of the scale inhibitor. The present invention does not specifically limit the pressurization operation. The present invention does not specifically limit the split ratio of the split flow, and those skilled in the art can adjust it according to actual needs.

[0084] After obtaining the first pressurized water, the first pressurized water enters the nanofiltration device 10 for nanofiltration, thereby obtaining the FPSO reinjection water. The present invention does not specifically limit the nanofiltration method. In the present invention, the nanofiltration method can remove salt from the pressurized water. In the present invention, the sulfate content in the FPSO reinjection water is preferably less than 20 mg / L, and the oxygen content is preferably less than 10 μg / L.

[0085] After obtaining the second pressurized water, the second pressurized water of the present invention enters the RO reverse osmosis device 11 for reverse osmosis to obtain reverse osmosis water. In the present invention, the reverse osmosis water is used for chemical cleaning and flushing of the ultrafiltration device 4 and the nanofiltration device 10.

[0086] The preparation method provided by the present invention uses bisulfite as a deoxidizer, which not only achieves deep deoxidation but also removes sodium hypochlorite through an oxidation-reduction reaction. Excess deoxidizer generated during the deoxidation process can be removed by a subsequent nanofiltration device, reducing the risk of excessive sulfate in FPSO reinjection water. The nanofiltration effluent obtained after nanofiltration can meet the FPSO reinjection water requirements. Therefore, there is no need to set up a reinjection water tank, saving floor space.

[0087] The system and method for preparing FPSO reinjection water provided by the present invention are described in detail below with reference to the embodiments, but they should not be construed as limiting the scope of protection of the present invention.

[0088] Example 1

[0089] exist Figure 1 The FPSO re-injection water is prepared in the schematic diagram shown in the figure. The specific process is as follows:

[0090] The seawater is extracted from 100 meters below the sea surface by the water pump 1, and the seawater is filtered by the coarse filter 3 (an automatic backwashing filter) to remove suspended solids, colloid, organic matter and the like, so as to obtain a coarse filtrate; the bactericide (sodium hypochlorite) is added into the obtained coarse filtrate by the bactericide adding device 2 to inhibit bacteria, so as to meet the water inlet requirement of the ultrafiltration device, and then the coarse filtrate is treated by the ultrafiltration device 4 (a horizontal ultrafiltration membrane, the flow and pressure of the ultrafiltration inlet are adjusted, so that the ultrafiltration effluent is a pressurized ultrafiltration liquid), so as to obtain the pressurized ultrafiltration liquid with a pressure of 0.2 MPa, and the content of hypochlorite in the pressurized ultrafiltration liquid is measured by the residual chlorine detector; the pressurized ultrafiltration liquid can directly enter the deoxidizing device 5 under the condition that there is no intermediate water tank and intermediate booster pump, and the deoxidizing agent (the deoxidizing agent is sodium bisulfite, and the sodium bisulfite is divided into a first part of sodium bisulfite and a second part of sodium bisulfite; the molar ratio of the first part of sodium bisulfite to the hypochlorite in the pressurized ultrafiltration liquid is 3:1; the addition amount of the second part of sodium bisulfite is 0.6 g / h per ton of seawater, which plays a role of a reducing agent in deep chemical deoxidization, neutralizes excessive bactericide, effectively protects the nanofiltration membrane in the nanofiltration device and the RO reverse osmosis membrane in the RO reverse osmosis device, and reduces the subsequent deoxidizing agent adding device; the addition amount of sodium bisulfite is determined according to the residual chlorine amount measured by the residual chlorine detector arranged after the ultrafiltration device, and the excessive deoxidizing agent is removed by the nanofiltration device 10, and will not cause the sulfate in the reinjection water to exceed the standard) is added into the deoxidizing device 5 by the deoxidizing agent adding device 6. The effluent of the deoxidizing device 5 is filtered by the security filter 7 and the scale inhibitor adding device 8 to add the scale inhibitor, so as to obtain a mixed system, the mixed system is branched, and the branched mixed system is pressurized by the first booster pump 9 and the second booster pump 12 respectively, so as to obtain the first pressurized water and the second pressurized water respectively, the first pressurized water directly enters the nanofiltration device 10, and the desalination of the nanofiltration device 10 can meet the requirement of the reinjection water (sulfate < 20 mg / L, oxygen content < 10 μg / L), so that the reinjection water tank is not needed and the reinjection water can be directly reinjected. The second pressurized water enters the RO reverse osmosis device 11 to perform reverse osmosis, so as to obtain the reverse osmosis water, and the reverse osmosis water is used for chemical cleaning, flushing and the like of the ultrafiltration device 4 and the nanofiltration device 10.

[0091] The above only describes the preferred embodiments of the present application, and it should be noted that the ordinary skilled in the art can make several improvements and refinements without departing from the principles of the present application, and these improvements and refinements should also be considered as the protection scope of the present application.

Claims

1. A system for preparing FPSO reinjection water, characterized in that: It includes a water intake pump (1); a coarse filter (3) in communication with the water outlet of the water intake pump (1); an ultrafiltration device (4) connected to the water outlet of the coarse filter (3), and a bactericide dosing device (2) is provided on the pipeline connecting the coarse filter (3) and the ultrafiltration device (4); a deoxidation device (5) in communication with the water outlet of the ultrafiltration device (4); a deoxidizer dosing device (6) in communication with the deoxidizer (5); a safety filter (7) in communication with the water outlet of the deoxidation device (5); A first booster pump (9) and a second booster pump (12) are respectively connected to the water outlet of the security filter (7); a scale inhibitor dosing device (8) is provided on the pipeline connecting the security filter (7) and the first booster pump (9) and the second booster pump (12); a nanofiltration device (10) connected to the water outlet of the first booster pump (9), an RO reverse osmosis device (11) in communication with the outlet water of the second booster pump (12); The ultrafiltration device (4) comprises an ultrafiltration inlet and a flow regulating valve arranged at the ultrafiltration inlet; The filter membrane used in the ultrafiltration device (4) is a horizontal ultrafiltration membrane.

2. The FPSO reinjection water preparation system according to claim 1, characterized in that: The coarse filter (3) is an automatic backwashing filter.

3. A method for preparing FPSO reinjection water using the preparation system according to claim 1 or 2, characterized in that: The following steps are involved: The seawater is extracted by a water pump (1) and enters a coarse filter (3) for coarse filtration to obtain a coarse filtrate; Adding a bactericide to the coarse filtrate through a bactericide dosing device (2) to sterilize the solution, thereby obtaining a sterilization system; The sterilization system enters the ultrafiltration device (4) for ultrafiltration to obtain a pressurized ultrafiltrate; The pressurized ultrafiltrate enters a deoxidation device (5), and a deoxidizer is added to the deoxidizer (5) through a deoxidizer dosing device (6) to perform deoxidation to obtain a deoxidized liquid; The deoxygenated liquid enters the safety filter (7) for safety filtration to obtain safety filtrate; The scale inhibitor is added through the scale inhibitor dosing device (8) and mixed with the security filtrate, and the resulting mixed system is split and pressurized by the first booster pump (9) and the second booster pump (12) respectively to obtain first pressurized water and second pressurized water respectively; The first pressurized water enters a nanofiltration device (10) for nanofiltration to obtain the FPSO reinjection water; The second pressurized water enters the RO reverse osmosis device (11) for reverse osmosis to obtain reverse osmosis water.

4. The method according to claim 3, characterized in that The bactericide includes sodium hypochlorite.

5. The method according to claim 3, characterized in that The pressure of the pressurized ultrafiltrate is 0.2 MPa.

6. The method according to claim 3, characterized in that The deoxidizer includes bisulfite.

7. The method according to claim 6, characterized in that The bisulfite includes sodium bisulfite.

8. The method according to claim 6, characterized in that The bisulfite comprises a first portion of bisulfite and a second portion of bisulfite; The molar ratio of the first portion of bisulfite to the hypochlorite in the pressurized ultrafiltrate is 3:1; The amount of the second portion of bisulfite added is 0.6 g / h per ton of seawater.

9. The method according to claim 3, 6, 7 or 8, characterized in that The deoxidation is carried out under spraying conditions, the deoxidation temperature is 18 to 40° C., and the deoxidation time is 2 to 10 minutes.

10. The method according to claim 3, characterized in that The sulfate content in the FPSO reinjection water is less than 20 mg / L, and the oxygen content is less than 10 μg / L.

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