A process and apparatus for water extraction and purification in complex oil-bearing production in offshore gas fields

Abstract

This invention discloses a process and apparatus for extracting and purifying complex oil-bearing production water from offshore gas fields. The complex oil-bearing production water from the offshore gas field first enters a production separator for three-phase separation of gas, oil, and water. The separated gas, oil, and water phases then enter a fuel gas treatment system, an oil treatment system, and a production water extraction and purification system for further processing, respectively. The water phase entering the production water extraction and purification system enters the extraction separator via a petal-type enhanced mixing unit and enters the countercurrent extraction chamber from the upper water phase inlet. Meanwhile, light condensate oil or condensate from the fuel gas treatment system and liquid light hydrocarbons from the oil treatment system serve as the extraction phase and enter the countercurrent extraction chamber from the lower extraction phase inlet of the extraction separator, further mixing and extracting with the water phase in the countercurrent extraction chamber. Combined with the aggregation and growth effect of the particulate extraction bed on the extract phase droplets, dissolved oil, emulsified oil, and dispersed oil in the water phase are effectively removed.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of environmental protection of oil sewage treatment, and particularly relates to a sea gas field complex oily production water extraction and purification process and device. BACKGROUND

[0002] At present, the treatment method of the sea gas field production water is that the well fluid enters the production separator for treatment, and then the oil, water and gas are separated, the production water flowing out of the production separator enters the hydrocyclone, and the water separated by the cyclone enters the flash tank for buffering and then is discharged into the sea. With the decrease of downhole pressure, the decrease of produced material and production operation pressure, and the increase of gas phase flow in the middle stage of the sea gas field exploitation, the production water is seriously emulsified, and the production water contains a large amount of dissolved oil. It is difficult to reach the reinjection or discharge standard by using the existing process and equipment to treat the production water.

[0003] CN110759566A discloses a sea gas field platform production water treatment method, which adds a coalescence oil removal device and a hydrocyclone in series or parallel on the basis of the original production water treatment system. The device can reduce the oil content of the discharged production water from several thousand to less than 30mg / L. However, the production water treated by the device still contains a large amount of dissolved oil, and the dissolved oil cannot be effectively removed.

[0004] CN113082765A discloses a high-pressure extraction device and a use method thereof. The device uses pressurization and rotating flow field to improve the extraction efficiency. However, the device needs to be driven by bearings to rotate, which has high energy consumption. In addition, the pressurization process puts higher requirements on the pressure resistance safety of the device, and is not suitable for occasions with large extraction treatment capacity. SUMMARY

[0005] In view of the above-mentioned shortcomings and deficiencies of the current sea gas field production water treatment method, the present application provides a sea gas field complex oily production water extraction and purification process and device.

[0006] To achieve the above-mentioned purpose, the present application adopts the following technical scheme:

[0007] A sea gas field complex oily production water extraction and purification process comprises the following steps:

[0008] S1: the complex oily production water from the sea gas field first enters the production separator, the production water is subjected to three-phase separation of gas, oil and water, and then the separated gas phase, oil phase and water phase enter the fuel gas treatment system, the oil treatment system and the production water extraction and purification system for further treatment. The treated gas phase is partly output as export gas, and the other part enters the flare system for treatment. The treated oil phase is output as export oil;

[0009] S2: The water phase entering the production water extraction purification system enters the extraction separator via the petal-shaped reinforced mixing unit for extraction purification. The water phase enters the water phase distributor via the water phase inlet at the upper part of the extraction separator, and then is uniformly distributed by the water phase distributor into the countercurrent extraction cavity in the extraction separator, and flows from top to bottom in the countercurrent extraction cavity;

[0010] S3: The light condensate or condensate liquid extracted from the fuel gas treatment system and the liquid light hydrocarbon extracted from the oil treatment system enter the extraction separator as the extraction phase. The extraction phase enters the droplet generator via the extraction phase inlet at the lower part of the extraction separator, generates a large number of uniform extraction phase droplets into the countercurrent extraction cavity, and flows from bottom to top in the countercurrent extraction cavity, and further mixes and extracts with the water phase in the countercurrent extraction cavity;

[0011] S4: After mixed extraction, the extraction phase in the countercurrent extraction cavity floats up through the fiber demisting bed layer in the extraction separator for demisting, while the fiber demisting bed layer allows the residual small amount of water phase in the extraction phase to coalesce, realizing the dehydration separation of the extraction phase. The extraction phase after demisting and dehydration continues to float up into the extraction phase settling chamber at the top of the extraction separator;

[0012] S5: After mixed extraction, the water phase in the countercurrent extraction cavity and the extraction phase carried in the water phase further pass through the particle extraction bed layer in the extraction separator downward. The particle extraction bed layer uses the coalescence capture effect of hydrophilic and oleophilic particles to make the extraction phase droplets grow, and the extraction phase droplets adhered to the particle extraction bed layer cause internal circulation flow of the extraction phase droplets under the shearing force of the water phase due to the relative velocity between the extraction phase droplets and the water phase, and capture the dissolved oil, emulsified oil and suspended oil in the water phase;

[0013] S6: The water phase passing through the particle extraction bed layer flows downward into the water phase settling chamber at the bottom of the extraction separator and flows out from the water phase outlet, obtaining purified water with dissolved oil, emulsified oil and suspended oil removed. The extraction phase passing through the particle extraction bed layer flows downward into the water phase settling chamber and floats and accumulates in the tapered section at the top of the water phase settling chamber;

[0014] S7: The extraction phase floating and accumulating in the tapered section at the bottom of the water phase settling chamber and the extraction phase in the extraction phase settling chamber are pumped by the circulation pump. Part of the extraction phase is regenerated, and the other part is input into the petal-shaped reinforced mixing unit as the circulating extraction phase.

[0015] According to the preferred embodiment of the present application, the droplet dispersion particle size of the extraction phase generated after passing through the extraction phase droplet generator is 0.05-2 mm.

[0016] According to the preferred embodiment of the present application, the petal-shaped reinforced mixing unit comprises a T-shaped jet mixing chamber, a jet top cone injector and a petal-shaped turbulence mixing chamber; the circulating extraction phase enters the jet top cone injector to generate fine extraction phase droplets which are uniformly mixed with the water phase in the jet mixing chamber, and at the same time, part of the dissolved oil, emulsified oil and dispersed oil in the extraction water is removed, and then enters the petal-shaped turbulence mixing chamber to strengthen the extraction effect, wherein:

[0017] The circulating extraction phase is dispersed into droplets with a particle size of 10-200 μm after passing through the jet top cone injector, and the extraction phase is dispersed into droplets with a particle size of 10-50 μm after passing through the petal-shaped turbulence mixing chamber.

[0018] A device for extracting and purifying complex oil-containing production water of offshore gas fields, comprising a production separator, a fuel gas treatment system, an oil treatment system and a production water extraction and purification system, wherein:

[0019] The production separator is used for separating oil, water and gas in the complex oil-containing production water of offshore gas fields, and the top of the production separator is provided with a gas phase outlet, the middle is provided with an oil phase outlet, and the bottom is provided with a water phase outlet, and the gas phase outlet, the oil phase outlet and the water phase outlet are connected to the fuel gas treatment system, the oil treatment system and the production water extraction and purification system, respectively;

[0020] The bottom of the fuel gas treatment system is provided with an oil phase outlet for collecting the produced light condensate oil or condensate liquid, and the oil phase outlet leads to the production water extraction and purification system as an extraction phase; the top of the fuel gas treatment system is provided with a fuel gas outlet, and a part of the separated fuel gas is led to a flare, and a part of the fuel gas is output as export gas;

[0021] The oil treatment system is provided with an oil phase outlet, and a part of the separated oil phase is output as export oil, and another part of the liquid light hydrocarbon is led into the production water extraction and purification system as an extraction phase through a pipeline;

[0022] The production water extraction and purification system comprises a petal-shaped reinforced mixing unit and an extraction separator connected in sequence, and a circulating pump connected between the extraction separator and the petal-shaped reinforced mixing unit;

[0023] The extraction separator comprises a countercurrent extraction chamber, an extraction phase settling chamber arranged above the countercurrent extraction chamber, and a water phase settling chamber arranged below the countercurrent extraction chamber; the inside of the countercurrent extraction chamber is sequentially provided from top to bottom with a fiber defoaming bed layer, a water phase distributor, a droplet generator, a particle extraction bed layer and a support layer.

[0024] According to the present application, the fiber defoaming bed layer is located at the top of the countercurrent extraction chamber, and is used for defoaming the extraction phase floating in the countercurrent extraction chamber, and allowing the residual small amount of water phase in the extraction phase to gather, so as to realize the dehydration separation of the extraction phase;

[0025] The water phase distributor is arranged below the fiber defoaming bed, and is used for distributing the produced water into the countercurrent extraction cavity;

[0026] The particle extraction bed is arranged at the bottom of the countercurrent extraction cavity, and is stacked by hydrophilic and oleophilic particles, and is used for capturing the extraction phase droplets in the water phase by the agglomeration of the hydrophilic and oleophilic particles, and is used for strengthening the extraction of the dissolved oil, emulsified oil and dispersed oil in the bed;

[0027] The droplet generator is arranged above the particle extraction bed, and is opposite to the water phase distributor, and is used for dispersing the extraction phase into droplets and then into the countercurrent extraction cavity;

[0028] The support layer is arranged at the bottom of the particle extraction bed, and is used for supporting the particle extraction bed.

[0029] According to the present application, the water phase distributor comprises a water phase flow guide pipe and a water phase distribution disc which are communicated with each other, the front end of the water phase flow guide pipe is communicated with the sewage inlet on the side wall of the countercurrent extraction cavity, and the rear end of the water phase flow guide pipe is communicated with the water phase distribution disc after being bent;

[0030] The water phase distribution disc comprises a circular ring segment which is distributed along the radial direction and a radial support segment which is used for supporting the circular ring segment, and the lower surfaces of the circular ring segment and the radial support segment are uniformly distributed with a plurality of columnar nozzles.

[0031] According to the preferred embodiment of the present application, the height of the columnar nozzle is 1-10 cm, and the inner diameter of the nozzle is 0.2-10 mm.

[0032] According to the preferred embodiment of the present application, the droplet generator comprises an extraction phase flow guide pipe and an extraction phase distribution disc which are communicated with each other, the front end of the extraction phase flow guide pipe is communicated with the extraction phase inlet on the side wall of the countercurrent extraction cavity, and the rear end of the extraction phase flow guide pipe is communicated with the extraction phase distribution disc after being bent;

[0033] The extraction phase distribution disc comprises a circular ring segment which is distributed along the radial direction and a radial support segment which is used for supporting the circular ring segment, and the lower surfaces of the circular ring segment and the radial support segment are uniformly distributed with a plurality of droplet generation columns.

[0034] According to the preferred embodiment of the present application, the droplet generation column comprises a tapering segment, a mixing segment, an expanding segment and a constant diameter segment which are arranged in sequence from the inlet to the outlet, and the tapering segment, the mixing segment, the expanding segment and the constant diameter segment are communicated with each other.

[0035] The tapering angle β of the tapering segment is 15°-45°, the outer wall of the mixing segment is uniformly distributed with a plurality of columnar nozzles, when the extraction phase passes through the droplet generation column, the external water phase is sucked into the columnar nozzles and mixed with the extraction phase by the negative pressure generated in the droplet generation column, the taper angle θ of the taper segment at the front end of the columnar nozzle is 10°-60°, and the expanding angle γ of the expanding segment is 5°-20°.

[0036] According to the preferred embodiment of the present application, the height of the droplet generation column is 1-10 cm; the inner diameter of the constant diameter section of the droplet generation column is 0.3-5 mm.

[0037] According to the preferred embodiment of the present application, the stacking ratio of the hydrophilic and oleophilic particles of the particle extraction bed is 1:4-4:1, and the porosity of the particle extraction bed is 20%-90%.

[0038] According to the present application, the main body of the water phase settling chamber is a cylindrical section, the bottom of which is provided with a water phase outlet, and the top of which is formed into a tapered section so that the upper end opening thereof matches the bottom opening of the countercurrent extraction cavity, and the tapered section is provided with an extraction phase outlet;

[0039] The main body of the extraction phase settling chamber is also a cylindrical section, the bottom of which is formed into a tapered section so that the bottom opening thereof matches the upper end opening of the countercurrent extraction cavity, and the tapered section is provided with an extraction phase outlet.

[0040] According to the present application, the tapering angle α of the tapered sections of the water phase settling chamber and the extraction phase settling chamber is 15°-60°.

[0041] According to the preferred embodiment of the present application, the petal-shaped reinforced mixing unit comprises a T-shaped jet mixing cavity, a jet top cone injector, and a petal-shaped turbulence mixing cavity, wherein:

[0042] One end of the horizontal section of the T-shaped jet mixing cavity is a water phase inlet, and the other end thereof is a mixed liquid outlet, and the vertical section thereof is an extraction phase inlet, the water phase inlet is connected with the water phase outlet of the production separator, the mixed liquid outlet is connected with the petal-shaped turbulence mixing cavity, the front end of the jet top cone injector is located in the extraction phase inlet, and the outlet of the petal-shaped turbulence mixing cavity is connected with the sewage inlet of the countercurrent extraction cavity.

[0043] According to the preferred embodiment of the present application, the jet top cone injector is composed of a hemispherical section at the front end and a column section at the rear end, the rear end of the column section is the extraction phase inlet, and the center of the hemispherical section is provided with a columnar injection port; the inside of the jet top cone injector is sequentially provided with a tapering port, an expanding port, and a top cone structure by means of a support structure of the inner wall of the injector from the circulating extraction phase inlet to the columnar injection port, wherein:

[0044] The tapering angle β1 of the tapering port is 15°-45°; and the expanding angle γ1 of the expanding port is 5°-20°;

[0045] The top cone angle θ1 of the top cone structure towards the extraction phase outlet is 45°-120°, and the tail cone angle θ2 of the top cone structure towards the extraction phase inlet is 15°-30°.

[0046] The present application has the following beneficial effects:

[0047] 1. The present application provides a complex offshore gas field oily production water extraction purification process and device by strengthening mixed mass transfer, the offshore gas field complex oily production water extraction purification device comprises a production separator, a fuel gas treatment system, an oil treatment system and a production water extraction purification system, the production water extraction purification system comprises an extraction separator and a petal type reinforced mixing unit; the offshore gas field complex oily production water extraction purification process uses condensate oil led out by the fuel gas treatment system and light hydrocarbon led out by the oil treatment system as an extraction phase to extract oil pollutants in production water, and separates the extraction phase from the water phase; the extraction phase and the water phase are premixed by an internal droplet generator in the extraction separator, and then the countercurrent mixing effect is used to further improve the extraction effect; combined with the coalescence and growth effect of the particle extraction bed on the extraction phase droplets, the internal circulation flow of the extraction phase droplets is caused under the shearing force of the water phase, and the oil pollutants in the water phase are captured for deep extraction and removal; after being pumped, a part of the extraction phase floating and gathered in the tapered section of the water phase settling chamber and located in the extraction phase settling chamber is sent to the oil treatment system, and the other part is input into the jet top cone injector as the circulating extraction phase, the circulating extraction phase entering the top cone injector is mixed with the water phase in the jet mixing chamber while extracting part of the oil pollutants in the water, and then enters the petal type turbulence mixing chamber for reinforced mixing and extraction.

[0048] 2. Compared with the traditional offshore gas field production water treatment system, the device of the present application can remove dissolved oil, emulsified oil and dispersed oil in water, has high extraction and separation efficiency, small process resistance, low energy consumption, and is suitable for the purification process of offshore gas field production water with serious emulsification, a large amount of dissolved oil and suspended oil. BRIEF DESCRIPTION OF DRAWINGS

[0049] Figure 1 It is a whole schematic view of the offshore gas field complex oily production water extraction purification device of the present application.

[0050] Figure 2 It is a schematic view of the production water extraction purification system structure in Figure 1 .

[0051] Figure 3 It is a structural schematic view of the extraction separator in Figure 2 .

[0052] Figure 4A and 4B are respectively the front view and the top view of the water phase distributor.

[0053] Figure 5A and 5B are respectively the front view and the top view of the droplet generator.

[0054] Figure 6This is a schematic diagram of the droplet generation column.

[0055] Figure 7 This is a schematic diagram of the structure of a petal-type enhanced hybrid unit.

[0056] Figure 8 This is a schematic diagram of the jet top cone ejector.

[0057] Figure 9 This is a schematic diagram of the apex cone structure.

[0058] Figure 10 This is a schematic diagram of the production water treatment modification scheme in Example 3. Detailed Implementation

[0059] The present invention will be further described in detail below with reference to embodiments. It should be understood that the following embodiments are only used to further illustrate the present invention and should not be construed as limiting the scope of protection of the present invention. Some non-substantial improvements and adjustments made by those skilled in the art based on the content of the present invention still fall within the scope of protection of the present invention.

[0060] Example 1: Water extraction and purification process and apparatus for complex oil-bearing production in offshore gas fields

[0061] 1.1 Water extraction and purification unit for complex oil-bearing production in offshore gas fields

[0062] like Figure 1 As shown, the offshore gas field complex oil-bearing production water extraction and purification device of the present invention includes a production separator 1, a fuel gas treatment system 2, an oil treatment system 3, and a production water extraction and purification system 4, wherein:

[0063] The production separator 1 is known in the prior art and is used for the three-phase separation of oil, water and gas in complex oil-bearing production water in offshore gas fields. The production separator 1 has a gas phase outlet at the top, an oil phase outlet in the middle, and a water phase outlet at the bottom. It is connected to the fuel gas treatment system 2, the oil treatment system 3 and the production water extraction and purification system 4 through the gas phase outlet, the oil phase outlet and the water phase outlet, respectively.

[0064] The bottom of the fuel gas treatment system 2 is provided with an oil phase outlet for collecting the generated light condensate oil or condensate and passing it to the production water extraction and purification system 4 as the extraction phase; the top of the system is provided with a fuel gas outlet, where part of the separated fuel gas goes to the flare and part is output as external gas.

[0065] The oil treatment system 3 is equipped with an oil phase outlet. A portion of the separated oil phase is exported as external oil, while the other portion of light hydrocarbons is piped into the production water extraction and purification system 4 as the extraction phase.

[0066] like Figure 2As shown in the figure, the production water extraction purification system 4 comprises a petal-shaped reinforced mixing unit 42 and an extraction separator 41 connected in sequence, and a circulating pump 43 connected between the extraction separator 41 and the petal-shaped reinforced mixing unit 42.

[0067] As shown in the figure, Figure 3 As shown in the figure, the extraction separator 41 comprises a countercurrent extraction cavity 411, an extraction phase settling chamber 418 arranged above the countercurrent extraction cavity 411, and a water phase settling chamber 416 arranged below the countercurrent extraction cavity 411; the inside of the countercurrent extraction cavity 411 is sequentially provided from top to bottom with a fiber defoaming bed layer 417, a water phase distributor 412, a droplet generator 413, a particle extraction bed layer 414, and a support layer 415, wherein:

[0068] The fiber defoaming bed layer 417 is located at the top of the countercurrent extraction cavity 411, and is used for defoaming the extraction phase floating up in the countercurrent extraction cavity 411, and allowing the residual small amount of water phase in the extraction phase to coalesce, so as to realize the dewatering separation of the extraction phase;

[0069] The water phase distributor 412 is arranged below the fiber defoaming bed layer 417, and is used for uniformly distributing the production water entering the extraction separator 41 into the countercurrent extraction cavity 411;

[0070] The droplet generator 413 is arranged above the particle extraction bed layer 414 and opposite to the water phase distributor 412, and is used for dispersing the extraction phase into droplets and then entering the countercurrent extraction cavity 411;

[0071] The particle extraction bed layer 414 is located at the bottom of the countercurrent extraction cavity 411, and is stacked by hydrophilic and oleophilic particles, and is used for capturing the extraction phase droplets in the water phase by the coalescence of the hydrophilic and oleophilic particles, and simultaneously strengthening the extraction of dissolved oil, emulsified oil and dispersed oil in the bed layer;

[0072] The support layer 415 is arranged at the bottom end of the countercurrent extraction cavity 411, and is used for supporting the particle extraction bed layer 414.

[0073] Further, as shown in the figure, Figure 4A As shown in the figure, the water phase distributor 412 comprises a water phase flow guide pipe 4121 and a water phase distribution disc 4122 in communication with each other, the front end of the water phase flow guide pipe 4121 is communicated with a sewage inlet on the side wall of the countercurrent extraction cavity 411, and the rear end after bending is communicated to the water phase distribution disc 4122. As shown in the figure, Figure 4B As shown in the figure, the water phase distribution disc 4122 comprises a circular ring segment 4123 distributed in the radial direction and a radial support segment 4124 for supporting the circular ring segment 4123; the lower surfaces of the circular ring segment 4123 and the radial support segment 4124 are uniformly distributed with a plurality of columnar nozzles 4125; preferably, the height of the columnar nozzle 4125 is 1-10 cm, and the inner diameter of the nozzle is 0.2-10 mm.

[0074] Further, as shown in Figure 5A The droplet generator 413 comprises an extraction phase guide pipe 4131 and an extraction phase distribution disc 4132 which are in communication with each other. The front end of the extraction phase guide pipe 4131 is connected to the extraction phase inlet on the side wall of the countercurrent extraction cavity 411, and the rear end after bending is connected to the extraction phase distribution disc 4132. As shown in Figure 5B The extraction phase distribution disc 4132 comprises a circular ring segment 4133 distributed in the radial direction and a radial support segment 4134 for supporting the circular ring segment 4133. The lower surfaces of the circular ring segment 4133 and the radial support segment 4134 are uniformly distributed with a plurality of droplet generation columns 4135.

[0075] Further, as shown in Figure 6 The droplet generation column 4135 comprises a tapered segment 4136, a mixing segment 4137, a gradually expanding segment 4139 and an equal diameter segment 4140 arranged in sequence from the inlet to the outlet. The tapering angle β of the tapered segment 4136 is 15°-45°. The outer wall of the mixing segment 4137 is uniformly distributed with a plurality of columnar taper openings 4138. When the extraction phase passes through the droplet generation column 4135, the external aqueous phase is sucked into the columnar taper opening 4138 and mixed with the extraction phase by using the negative pressure generated in the droplet generation column 4135. The taper angle θ of the taper segment at the front end of the columnar taper opening 4138 is 10°-60°. The gradually expanding angle γ of the gradually expanding segment 4139 is 5°-20°. The height of the droplet generation column 4135 is 1-10 cm. The inner diameter of the equal diameter segment 4140 of the droplet generation column 4135 is 0.3-5 mm.

[0076] Further, the particle extraction bed 414 is randomly stacked with hydrophilic and oleophilic particles. The hydrophilic particles can be selected from quartz sand, stainless steel, etc. The oleophilic particles can be selected from PTFE, nylon, polypropylene, etc. Preferably, the stacking ratio of the hydrophilic and oleophilic particles is 1:4-4:1. The porosity of the particle extraction bed 414 is 20%-90%.

[0077] Back to Figure 3 The main body of the aqueous phase settling chamber 416 is a cylindrical segment, and the bottom is provided with an aqueous phase outlet. The top is formed into a tapered segment so that the upper end opening matches the bottom opening of the countercurrent extraction cavity 411, and the tapered segment is provided with an extraction phase outlet.

[0078] Further, the main body of the extraction phase settling chamber 418 is also a cylindrical segment, and the bottom is formed into a tapered segment so that the bottom opening matches the upper end opening of the countercurrent extraction cavity 411, and the tapered segment is provided with an extraction phase outlet.

[0079] Preferably, the taper angle a of the tapered section of the water phase settling chamber 416 and the extraction phase settling chamber 418 is 15°-60°.

[0080] As shown in Figure 7 , the lobed turbulence mixing unit 42 comprises a T-shaped jet mixing chamber 421, a jet top cone injector 422 and a lobed turbulence mixing chamber 423, wherein one end of the horizontal section of the T-shaped jet mixing chamber 421 is the water phase inlet 4211 and the other end is the mixed liquid outlet 4213, and the vertical section is the extraction phase inlet 4212, the water phase inlet 4211 is connected with the water phase outlet of the production separator 1, the mixed liquid outlet 4213 is connected with the inlet 4231 of the lobed turbulence mixing chamber 423, the front end of the jet top cone injector 422 is located in the extraction phase inlet 4212, and the outlet 4234 of the lobed turbulence mixing chamber 423 is connected with the sewage inlet of the countercurrent extraction chamber 411.

[0081] Further, as shown in Figure 8 , the jet top cone injector 422 is composed of a front hemispherical section and a rear cylindrical section, the rear end of the cylindrical section is the extraction phase inlet, and the center of the hemispherical section is provided with a cylindrical injection port 4225; the inside of the jet top cone injector 422 is sequentially provided with a tapered port 4221, an expanding port 4222 and a top cone structure 4223 by means of a support structure 4224 in the inner wall of the injector from the circulating extraction phase inlet to the cylindrical injection port 4225; the taper angle b1 of the tapered port 4221 is 15°-45°; the expansion angle g1 of the expanding port 4222 is 5°-20°; as shown in Figure 9 , the cone top angle of the top cone structure 4223 towards the extraction phase outlet is 45°-120°, and the cone tail angle towards the extraction phase inlet is 15°-30°.

[0082] Further, back to Figure 7 , the inside of the lobed turbulence mixing chamber 423 is alternately provided with backflow lobes 4232 and oncoming flow lobes 4233, Figure 7 The arrows in the figure show the flow direction of the mixed flow.

[0083] 1.2, offshore gas field complex oily produced water extraction purification process

[0084] The offshore gas field complex oily produced water extraction purification process using the above device comprises the following steps:

[0085] S1: The complex oily production water from offshore gas field enters the production separator 1, and the production water is separated into gas, oil and water phases: then the separated gas, oil and water phases enter the fuel gas treatment system 2, the oil treatment system 3 and the production water extraction purification system 4 for further treatment respectively; the treated gas is output as export gas, and the treated oil is output as export oil;

[0086] S2: The water phase entering the production water extraction purification system 4 enters the extraction separator 41 through the petal-shaped enhanced mixing unit 42 for extraction purification: the water phase enters the water phase distributor 412 through the water phase inlet on the upper part of the extraction separator 41, and then is uniformly distributed into the countercurrent extraction cavity 411 of the extraction separator 41 by the water phase distributor 412, and flows from top to bottom in the countercurrent extraction cavity 411;

[0087] S3: The light condensate oil or condensate liquid drawn from the fuel gas treatment system 2 and the liquid light hydrocarbon drawn from the oil treatment system 3 enter the extraction separator 41 as extraction phase: the extraction phase enters the droplet generator 413 through the extraction phase inlet on the lower part of the extraction separator 41, a large number of uniform extraction phase droplets are generated and enter the countercurrent extraction cavity 411, and flow from bottom to top in the countercurrent extraction cavity 411, and further mix and extract with the water phase in the countercurrent extraction cavity 411;

[0088] S4: After mixed extraction, the extraction phase in the countercurrent extraction cavity 411 floats up through the fiber demisting bed layer 417 in the extraction separator 41 for demisting, and at the same time, the fiber demisting bed layer 417 causes the residual small amount of water phase in the extraction phase to coalesce, so as to realize the dehydration separation of the extraction phase; the extraction phase after demisting and dehydration continues to float up into the extraction phase settling chamber 418 at the top of the extraction separator 41;

[0089] S5: After mixed extraction, the water phase and the extraction phase carried in the water phase in the countercurrent extraction cavity 411 further pass through the particle extraction bed layer 414 in the extraction separator 41 downward, the extraction phase droplets adhered to the particle extraction bed layer 414 grow in size by the coalescence capture effect of the hydrophilic and oleophilic particles in the particle extraction bed layer 414, and the extraction phase droplets adhered to the particle extraction bed layer 414 cause internal circulation flow of the extraction phase droplets under the shearing force of the water phase due to the relative velocity between the extraction phase droplets and the water phase, and capture the dissolved oil, emulsified oil and suspended oil in the water phase;

[0090] S6: The water phase passing through the particle extraction bed layer 414 flows out from the water phase outlet after entering the water phase settling chamber 416 at the bottom of the extraction separator 41, and the purified water in which the dissolved oil, emulsified oil and suspended oil are removed is obtained; the extraction phase passing through the particle extraction bed layer 414 floats and gathers in the tapered section at the top of the water phase settling chamber 416;

[0091] S7: The tapered section of the water phase settling chamber 416 and the extraction phase of the extraction phase settling chamber 418 are pumped by the circulating pump 43, and a part of the extraction phase is regenerated, and the other part is input into the petal-shaped intensified mixing unit 42 as the circulating extraction phase.

[0092] Further, the dispersed particle size of the liquid droplets generated after the extraction phase passes through the extraction phase liquid droplet generator 413 is 0.05-2 mm.

[0093] Further, the petal-shaped intensified mixing unit comprises a T-shaped jet mixing chamber, a jet top cone sprayer, and a petal-shaped turbulence mixing chamber; the circulating extraction phase enters the jet top cone sprayer to generate fine extraction phase liquid droplets which are uniformly mixed with the water phase in the jet mixing chamber, and at the same time, part of the dissolved oil, emulsified oil, and dispersed oil in the water phase is extracted, and then enters the petal-shaped turbulence mixing chamber to intensify the extraction effect, wherein:

[0094] The circulating extraction phase is dispersed into liquid droplets with a particle size of 10-200 μm after passing through the jet top cone sprayer 422, and the extraction phase is dispersed into liquid droplets with a particle size of 10-50 μm after passing through the petal-shaped turbulence mixing chamber 423.

[0095] Further, the oil content in the inlet water of the production water extraction and purification system 4 is 1000-5000 mg / L; the oil content at the outlet of the water phase of the production water extraction and purification system 4 is <20 mg / L, reaching the discharge and reinjection standards.

[0096] Example 2,

[0097] The production water treatment process of a certain offshore gas field platform is subjected to a pilot test by using the process and device of the present application, and the production water treatment process flow chart of the test is shown in Figure 1 .

[0098] The test treatment capacity is 5 m 3 / h, the oil content of the production water flowing out of the production separator 1 is about 1300 mg / L, the light condensate oil introduced by the fuel gas treatment system 2 is about 0.4 m 3 / h, and the light condensate oil introduced by the oil treatment system 3 is about 0.1 m 3 / h, and the running effect of the test equipment is shown in Table 1 below.

[0099] Table 1

[0100]

[0101]

[0102] As shown by the results in Table 1, by using the device and process of the present application, the overall oil content of the outlet water is lower than 20 mg / L, and the oil removal efficiency in the production water is higher than 98%.

[0103] Example 3,

[0104] A certain offshore gas field platform, using the process and device of the present application to transform the production water treatment scheme, as shown in Figure 10

[0105] The platform uses two-stage production separator to separate oil, gas and water, and the original process uses a cyclone for the purification of production water. However, with the increase of oil content in the production water at the outlet of the production separator, the separation effect of the cyclone cannot meet the requirements of the production water for discharge to sea.

[0106] After process transformation, the production water at the outlet of the first and second stage production water separators of the platform is collected into the production water extraction and purification system as the water phase to be treated, and the light condensate oil collected in the scrubber is used as the extraction phase. The average oil content of the production water at the inlet of the production water extraction and purification system is about 3000 mg / L. The running test effect after transformation using the process and device of the present application is shown in Table 2 below.

[0107] Table 2

[0108]

[0109] Result analysis: The original production water treatment uses a cyclone, and the oil content of the production water at the outlet is maintained at 100-250 mg / L, which is far from meeting the requirements for discharge to sea and reinjection. After oil removal by the production water extraction and purification device of the present application, the oil content in the production water can be stably maintained below 20 mg / L, meeting the standards for discharge to sea and reinjection.​

Claims

1. A process for the purification of complex produced water from offshore oil and gas fields by extraction with an oil, characterized in that, The method comprises the following steps: S1: the complex oil-containing production water from the offshore gas field first enters a production separator for three-phase separation of gas, oil and water, and then the separated gas phase, oil phase and water phase enter a fuel gas treatment system, an oil treatment system and a production water extraction purification system respectively for further treatment, and the treated gas phase is partly output as export gas and the other part enters a flare system for treatment, and the treated oil phase is output as export oil; S2: the water phase entering the production water extraction purification system enters an extraction separator through a petal-shaped enhanced mixing unit for extraction purification, the water phase enters a water phase distributor through a water phase inlet at the upper part of the extraction separator, and then is uniformly distributed into the countercurrent extraction cavity in the extraction separator by the water phase distributor and flows from top to bottom in the countercurrent extraction cavity; The petal-shaped enhanced mixing unit comprises a T-shaped jet mixing cavity, a jet top cone injector and a petal-shaped turbulence mixing cavity; after the circulating extraction phase enters the jet top cone injector, fine extraction phase droplets are generated and uniformly mixed with the water phase in the jet mixing cavity, and at the same time, part of the dissolved oil, emulsified oil and dispersed oil in the extraction water is extracted, and then enters the petal-shaped turbulence mixing cavity for enhanced extraction; S3: light condensate oil or condensate liquid extracted from the fuel gas treatment system and liquid light hydrocarbon extracted from the oil treatment system enter the extraction separator as extraction phases, the extraction phases enter a droplet generator through an extraction phase inlet at the lower part of the extraction separator, a large number of uniform extraction phase droplets are generated and enter the countercurrent extraction cavity, and flow from bottom to top in the countercurrent extraction cavity to further mix and extract with the water phase in the countercurrent extraction cavity; The droplet generator comprises an extraction phase flow guide pipe and an extraction phase distribution disc in communication, the extraction phase distribution disc comprises a circular ring segment distributed in the radial direction and a radial support segment for supporting the circular ring segment; the lower surfaces of the circular ring segment and the radial support segment are uniformly distributed with a plurality of droplet generation columns; the droplet generation column comprises a tapered section, a mixing section, an expanding section and an equal-diameter section arranged in sequence from the inlet to the outlet, and a plurality of column cone ports are uniformly distributed on the outer wall of the mixing section; when the extraction phase passes through the droplet generation column, the external water phase is sucked into the column cone port and mixed with the extraction phase by using the negative pressure generated in the droplet generation column; S4: after the mixed extraction, the extraction phase floating in the countercurrent extraction cavity passes through a fiber demisting bed layer in the extraction separator for demisting, and at the same time, the fiber demisting bed layer causes the residual small amount of water phase in the extraction phase to coalesce, so as to realize the dehydration separation of the extraction phase; the extraction phase after demisting and dehydration continues to float into an extraction phase settling chamber at the top of the extraction separator; S5: after the mixed extraction, the water phase and the extraction phase carried in the water phase in the countercurrent extraction cavity further pass through a particle extraction bed layer in the extraction separator, the extraction phase droplets are caused to grow by using the coalescence and capture effect of the hydrophilic and oleophilic particles in the particle extraction bed layer, and at the same time, the extraction phase droplets adhered to the particle extraction bed layer cause the internal circulation flow of the extraction phase droplets due to the relative velocity with the water phase under the shearing force of the water phase, and capture the dissolved oil, emulsified oil and suspended oil in the water phase. S6: the water phase passing through the granular extraction bed layer downwardly into the water phase settling chamber at the bottom of the extraction separator flows out from the water phase outlet, obtaining purified water removing dissolved oil, emulsified oil and suspended oil; the extraction phase passing through the granular extraction bed layer downwardly into the water phase settling chamber floats and gathers at the tapered section at the top of the water phase settling chamber; S7: the extraction phase and the extraction phase in the extraction phase settling chamber floating and gathering at the tapered section at the bottom of the water phase settling chamber are pumped by the circulating pump, part of the extraction phase is regenerated, and the other part is input into the lobed enhanced mixing unit as the circulating extraction phase.

2. The extraction purification process of claim 1, wherein, The dispersed particle size of the liquid droplets generated by the extraction phase after passing through the extraction phase liquid droplet generator is 0.05-2mm.

3. The extraction purification process of claim 1, wherein, In the lobed enhanced mixing unit: The circulating extraction phase is dispersed into liquid droplets with a particle size of 10-200μm after passing through the jet top cone injector, and the extraction phase is dispersed into liquid droplets with a particle size of 10-50μm after passing through the lobed turbulent mixing cavity.

4. A complex offshore gas field oily production water extraction and purification unit, characterized in that, The device comprises a production separator, a fuel gas treatment system, an oil treatment system and a production water extraction purification system, wherein: The production separator is used for three-phase separation of oil, water and gas of complex oil-containing production water in offshore gas fields, the top of the production separator is provided with a gas phase outlet, the middle is provided with an oil phase outlet, and the bottom is provided with a water phase outlet, and the gas phase outlet, the oil phase outlet and the water phase outlet are connected with the fuel gas treatment system, the oil treatment system and the production water extraction purification system respectively; The bottom of the fuel gas treatment system is provided with an oil phase outlet for collecting produced light condensate oil or condensate liquid, and leading to the production water extraction purification system as an extraction phase; the top of the fuel gas treatment system is provided with a fuel gas outlet, part of the separated fuel gas is led to a flare, and part is output as export gas; The oil treatment system is provided with an oil phase outlet, part of the separated oil phase is output as export oil, and another part of the liquid light hydrocarbon is led into the production water extraction purification system as an extraction phase through a pipeline; The production water extraction purification system comprises a lobed enhanced mixing unit and an extraction separator connected in sequence, and a circulating pump connected between the extraction separator and the lobed enhanced mixing unit; The lobed enhanced mixing unit comprises a T-shaped jet mixing cavity, a jet top cone injector and a lobed turbulent mixing cavity, wherein: One end of the horizontal section of the T-shaped jet mixing cavity is a water phase inlet, and the other end is a mixed liquid outlet, the vertical section is an extraction phase inlet, the water phase inlet is connected with the water phase outlet of the production separator, the mixed liquid outlet is connected with the lobed turbulent mixing cavity, the front end of the jet top cone injector is located in the extraction phase inlet, and the outlet of the lobed turbulent mixing cavity is connected with the sewage inlet of the countercurrent extraction cavity; The extraction separator comprises a countercurrent extraction cavity, an extraction phase settling chamber arranged above the countercurrent extraction cavity and a water phase settling chamber arranged below the countercurrent extraction cavity; the inside of the countercurrent extraction cavity is sequentially provided with a fiber demisting bed layer, a water phase distributor, a liquid droplet generator, a granular extraction bed layer and a support layer from top to bottom. The droplet generator comprises an extraction phase guide pipe and an extraction phase distribution disc which are in communication with each other, the front end of the extraction phase guide pipe is communicated with the extraction phase inlet on the side wall of the countercurrent extraction cavity, and the rear end after being bent is communicated to the extraction phase distribution disc; the extraction phase distribution disc comprises a circular ring segment distributed in the radial direction and a radial support segment for supporting the circular ring segment; the lower surfaces of the circular ring segment and the radial support segment are uniformly distributed with a plurality of droplet generation columns; The droplet generation column comprises a tapering segment, a mixing segment, an expanding segment and a constant diameter segment which are sequentially arranged from the inlet to the outlet, and a plurality of columnar orifices are uniformly distributed on the outer wall of the mixing segment.

5. The extraction purification device according to claim 4, characterized in that: The fiber defoaming bed is located at the top of the countercurrent extraction cavity, is used for defoaming the extraction phase floating in the countercurrent extraction cavity, and allows the residual small amount of water phase in the extraction phase to gather, so as to realize the dehydration separation of the extraction phase; The water phase distributor is arranged below the fiber defoaming bed, is used for distributing the production water entering the extraction separator into the countercurrent extraction cavity; The particle extraction bed is located at the bottom of the countercurrent extraction cavity, is stacked by hydrophilic and oleophilic particles, captures the extraction phase droplets in the water phase by using the coalescence of the hydrophilic and oleophilic particles, and strengthens the extraction of dissolved oil, emulsified oil and dispersed oil in the bed; The droplet generator is arranged above the particle extraction bed, is opposite to the water phase distributor, and is used for dispersing the extraction phase into droplets and then entering the countercurrent extraction cavity; The support layer is arranged at the bottom of the particle extraction bed, and is used for supporting the particle extraction bed.

6. The extraction purification device according to claim 4 or 5, characterized in that The water phase distributor comprises a water phase guide pipe and a water phase distribution disc which are in communication with each other, the front end of the water phase guide pipe is communicated with the sewage inlet on the side wall of the countercurrent extraction cavity, and the rear end after being bent is communicated to the water phase distribution disc; The water phase distribution disc comprises a circular ring segment distributed in the radial direction and a radial support segment for supporting the circular ring segment; the lower surfaces of the circular ring segment and the radial support segment are uniformly distributed with a plurality of columnar nozzles.

7. The extraction purification device according to claim 6, characterized in that The height of the columnar nozzle is 1-10 cm, and the inner diameter of the nozzle is 0.2-10 mm.

8. The extraction purification device according to claim 4, characterized in that: In the droplet generation column, the tapering angle β of the tapering segment is 15-45°; when the extraction phase passes through the droplet generation column, the external water phase is sucked into the columnar orifice and mixed with the extraction phase by using the negative pressure generated in the droplet generation column, the tapering angle θ of the tapering segment at the front end of the columnar orifice is 10-60°; and the expanding angle γ of the expanding segment is 5-20°.

9. The extraction purification device according to claim 4 or 8, characterized in that The height of the droplet generation column is 1-10 cm; and the inner diameter of the constant diameter segment of the droplet generation column is 0.3-5 mm.

10. The extraction purification device of claim 4, wherein, The stacking ratio of the hydrophilic and oleophilic particles in the particle extraction bed is 1:4-4:1, and the porosity of the particle extraction bed is 20%-90%.

11. The extraction purification device according to claim 4, characterized in that: The main body of the water phase settling chamber is a columnar segment, the bottom of the main body is provided with a water phase outlet, the top of the main body is formed into a tapering segment, the upper end opening of the tapering segment is matched with the bottom opening of the countercurrent extraction cavity, and the tapering segment is provided with an extraction phase outlet. The main body of the extraction phase settling chamber is also a cylindrical section, the bottom of which is formed into a tapered section to match the opening of the bottom of the countercurrent extraction cavity, and the tapered section is provided with an extraction phase outlet.

12. The extraction purification device of claim 4, wherein, The tapering angle α of the tapered sections of the water phase settling chamber and the extraction phase settling chamber is 15°-60°.

13. The extraction purification device of claim 4, wherein, The jet top cone injector is composed of a hemispherical section at the front end and a cylindrical section at the rear end, the rear end of the cylindrical section being the extraction phase inlet, and the center of the hemispherical section being provided with a cylindrical injection port; the inside of the jet top cone injector is sequentially provided with a tapering port, an expanding port, and a top cone structure provided by means of a support structure of the inner wall of the injector from the circulating extraction phase inlet to the cylindrical injection port, wherein: The tapering angle β1 of the tapering port is 15°-45°; and the expanding angle γ1 of the expanding port is 5°-20°; The top cone structure has a cone top angle θ1 of 45°-120° toward the extraction phase outlet and a cone tail angle θ2 of 15°-30° toward the extraction phase inlet.

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