Oilfield produced fluid pretreatment device

Abstract

This invention discloses an oilfield produced fluid pretreatment device, comprising: a magnetic separation unit, which is a cylindrical structure with multiple layers of magnetically concentrated media inside, which adsorb solid suspended matter in the produced fluid through the action of a magnetic field; and an oil-water deep separation unit, which receives the produced fluid after magnetic separation and preliminary oil-water separation and performs deep oil-water separation. The deep oil-water separation unit includes an oil phase dehydration subunit, which is equipped with multiple layers of annularly spaced electrode plates and coalescing packing. The oil phase of the produced fluid flows sequentially through the multiple layers of coalescing packing, and under the action of the electric field and the coalescing packing, tiny water droplets in the oil phase coalesce into larger droplets. This invention can effectively remove solid suspended impurities from the produced fluid and simultaneously achieve deep oil-water separation, solving the problems of complex produced fluid treatment processes, large amounts of demulsifiers, and low separation efficiency in existing technologies. The treatment process is more efficient and environmentally friendly, and the wastewater can directly meet the reinjection water standards, reducing the investment cost of produced fluid treatment.

Description

Technical Field

[0001] This invention relates to the field of petrochemical technology, and in particular to an oilfield produced fluid pretreatment device. Background Technology

[0002] With the increasing demand for oil resources and the continuous increase in crude oil extraction, the trend of heavier and lower-quality crude oil both domestically and internationally has intensified. In particular, as major oilfields enter the tertiary oil recovery stage, the implementation of enhanced oil recovery technologies such as chemical flooding (polymer flooding, surfactant flooding, ternary composite flooding, etc.) and production enhancement measures such as acidizing and fracturing has led to increasingly higher water content in oilfield produced fluids. This necessitates demulsification to achieve oil-water separation, followed by crude oil dehydration for external transportation and wastewater deoiling for reinjection.

[0003] The existing oilfield produced fluid treatment process is as follows: 1) Oilfield produced fluid → oil-water separator → (add emulsifier) ​​→ hydrocyclone → reinjection water; 2) Oilfield produced fluid → electrostatic desalting unit → API oil-water separator → CPI oil-water separator → IGF flotation → effluent; 3) Oilfield produced fluid → oil-water separator → hydrocyclone → primary filtration → stripping tower desulfurization → lime water softening → secondary filtration → cation exchange → steam boiler. The above processes have problems such as high chemical consumption, large amount of demulsifier added, low separation efficiency, and complex process flow.

[0004] In recent years, the development of enhanced separation technologies, such as multi-physics coupling, has received widespread attention. Among these, the coupling of cyclone centrifugation and electric fields has been extensively studied. The combined effect of the cyclone field and the electric field can significantly improve the separation performance of water-in-oil emulsions, but its separation depth is insufficient. For example, Chinese patent application CN107937019A discloses a pipeline-type electric field coalescing oil-water separation device, including a dewatering pipe with oil-water inlet and outlet. The dewatering pipe has one or more sets of dewatering holes along its axial direction, with the outer circumferential surface of the holes tangent to the inner wall of the pipe. The dewatering pipe contains a first electrode and a second electrode; the first electrode is connected to the positive terminal of a power supply, and the second electrode is connected to the negative terminal. This device can be used to demulsify or pre-coalesce produced fluids under electric fields. However, this method is not ideal for separating small-sized dispersed droplets, and under the residence time conditions of most industrial applications, it cannot achieve deep demulsification and separation of oil and water in a single treatment.

[0005] The information disclosed in this background section is intended only to enhance the understanding of the overall background of the invention and should not be construed as an admission or in any way implying that the information constitutes prior art known to those skilled in the art. Summary of the Invention

[0006] The purpose of this invention is to provide an oilfield produced fluid pretreatment device that can not only effectively remove solid suspended impurities from the produced fluid, but also achieve deep oil-water separation at the same time. This solves the problems of complex produced fluid treatment processes, large amounts of demulsifiers, and low separation efficiency in the prior art. The treatment process is more efficient and green, and the wastewater can directly meet the reinjection water standards, thus reducing the investment cost of produced fluid treatment.

[0007] To achieve the above objectives, the present invention provides an oilfield produced fluid pretreatment device, comprising: a magnetic separation unit, which is a cylindrical structure and has multiple layers of magnetically concentrated media inside, which adsorb solid suspended matter in the produced fluid through the action of a magnetic field; an oil-water deep separation unit, which receives the produced fluid after magnetic separation and preliminary oil-water separation, and performs deep oil-water separation; the oil-water deep separation unit includes an oil phase dehydration subunit, which is provided with multiple layers of annularly spaced electrode plates and coalescing packing, the oil phase of the produced fluid flows through the multiple layers of coalescing packing in sequence, and under the action of an electric field and coalescing packing, the tiny water droplets in the oil phase coalesce into larger water droplets.

[0008] Furthermore, in the above technical solution, the multi-layered annularly spaced electrode plates may include: a first electrode plate, which is annularly arranged and located on the outermost layer; a second electrode plate, which is annularly arranged and located inside the first electrode plate, with a first cavity between the first and second electrode plates, the first cavity being filled with a first coalescing filler; a third electrode plate, which is annularly arranged and located inside the second electrode plate, with a second cavity between the second and third electrode plates, the second cavity being filled with a second coalescing filler; and a third cavity inside the third electrode plate, the third cavity being filled with a third coalescing filler.

[0009] Furthermore, in the above technical solution, the oil phase of the produced fluid flows sequentially and back through the first coalescing packing, the second coalescing packing, and the third coalescing packing, with the packing precision increasing sequentially.

[0010] Furthermore, in the above technical solution, an alternating current can be applied between the first electrode plate, the second electrode plate, and the third electrode plate; the electric field strength in the first cavity is 350–450 V / cm; and the electric field strength in the second cavity is 800–1500 V / cm.

[0011] Furthermore, in the above technical solution, the oil-water deep separation unit may also include an aqueous phase oil removal subunit. In this aqueous phase oil removal subunit, multi-stage structured fiber packing is arranged along the direction of aqueous phase flow. The fiber packing is filled in a multi-layer stacked manner, and the packing precision increases sequentially along the direction of aqueous phase flow.

[0012] Furthermore, in the above technical solution, the first coalescing filler, the second coalescing filler, and the third coalescing filler can be woven from hydrophilic and oleophobic polypropylene fibers in a 3:1 ratio.

[0013] Furthermore, in the above technical solution, the structured fiber filler can be woven from a mixture of oleophilic and hydrophobic polypropylene fibers and hydrophilic and oleophobic polypropylene fibers in a 4:1 ratio.

[0014] Furthermore, in the above technical solution, the magnetic separation unit receives the extracted liquid that has been heated and injected with flocculant and magnetic seeds. A high gradient magnetic field is formed inside the cylindrical structure by a magnetic field generating device outside the cylindrical structure. Under the action of the high gradient magnetic field, the flocculent precipitate with magnetic seeds as the core is adsorbed by the magnetic medium.

[0015] Furthermore, in the above technical solution, the cylindrical structure can be an aluminum cylinder, and the magnetic medium can be a stainless steel grid.

[0016] Furthermore, in the above technical solution, the diameter of the stainless steel wires in the grille can be 0.45 to 0.55 mm; the spacing between the stainless steel wires can be set to 1.5 to 2.5 mm; and the spacing between adjacent grille layers can be set to 10 to 15 mm.

[0017] Furthermore, in the above technical solution, the stainless steel wires of adjacent layers of grid can be arranged in staggered directions; the included angle between the extension directions can be 0 to 90°.

[0018] Furthermore, in the above technical solution, the magnetic field generating device may include: a first magnet disposed on the outer wall of the aluminum cylinder for generating a uniform magnetic field distributed in the vertical direction within the aluminum cylinder; and a second magnet disposed outside the first magnet for generating a uniform magnetic field distributed in the horizontal direction within the aluminum cylinder.

[0019] Furthermore, in the above technical solution, the first magnet is an electromagnetic induction coil wound around the outer wall of an aluminum cylinder; the second magnet is a magnetic outer cylinder composed of electromagnets; a uniform magnetic field in the vertical direction and a uniform magnetic field in the horizontal direction are generated alternately to drive the flocculent precipitate with magnetic seeds as the core to be uniformly adsorbed on each layer of grid.

[0020] Furthermore, in the above technical solution, the outer cylinder of the magnet can be made of copper wire wound around a ring-shaped iron core.

[0021] Furthermore, in the above technical solution, the magnetic field strength of the vertical uniform magnetic field and the horizontal uniform magnetic field can be 0.6T, and the alternation time between the two is 60 to 180s.

[0022] Furthermore, in the above technical solution, the oilfield produced fluid pretreatment device may also include: a gas-liquid separation unit, which is set at the front end of the magnetic separation unit. The produced fluid enters the wall of the gas-liquid separation unit tangentially, and the produced fluid is separated into gas and liquid by the difference in centrifugal force between gas and liquid.

[0023] Furthermore, in the above technical solution, the oilfield produced fluid pretreatment device may also include: an oil-water preliminary separation unit, which is set between the magnetic separation unit and the oil-water deep separation unit, and performs preliminary separation of oil and water by means of swirling flow and the difference in oil and water density.

[0024] Furthermore, in the above technical solution, the oilfield produced fluid pretreatment device may also include: a sedimentation unit, which is located at the rear end of the oil-water deep separation unit, and is used to sediment and separate the produced fluid after oil phase dehydration and water phase oil removal treatment.

[0025] Compared with the prior art, the present invention has the following beneficial effects:

[0026] 1) The magnetic separation unit in the device of the present invention has a built-in layered grid in an aluminum cylinder, and the stainless steel wires of each layer of grid are arranged at an angle to make it less likely to be blocked when the produced fluid passes through. The grid is placed in a magnetic field and magnetized, and its surface can generate a high gradient magnetic field, so that the solid particles in the produced fluid are mixed evenly with the magnetic seeds and flocculants to form flocculent precipitates with the magnetic seeds as the core. The flocculent precipitates are adsorbed onto the grid, thus realizing the effective separation of solid suspended matter in the produced fluid.

[0027] 2) The two magnetic field generating devices in the magnetic separation unit work alternately, which makes the magnetic field strength between the stainless steel wire grid in the aluminum cylinder alternately increase, making the adsorption of each grid layer more uniform. This prevents a large number of particles from directly staying in the first grid layer and being unable to flow downwards, thus causing the aluminum cylinder to become blocked in advance before reaching overall adsorption saturation.

[0028] 3) In the oil-water deep separation unit of this invention, during the oil phase dehydration process, the electric field drives the rapid migration of tiny water droplets. Utilizing the media interception and wetting coalescing effects, a wide range of media sites are provided for droplet coalescence, solving the problem of low droplet collision interception efficiency in electric field coalescence. Through the combined action of the electric field and the coalescence field, tiny water droplets more easily coalesce into larger droplets, which are then separated during subsequent sedimentation, achieving deep dehydration of the oil phase. The oil phase dehydration process employs physical demulsification, offering advantages such as high efficiency, energy saving, and environmental friendliness.

[0029] 4) In the oil-water deep separation unit of the device of this invention, during the aqueous phase oil removal process, a structured fiber packing is used for coalescence. The packing is arranged in stages and assembled from a mixture of oleophilic and hydrophobic fibers woven into a certain structure. Small oil droplets in the produced fluid from the oilfield entering the packing are more easily coalesced into larger oil droplets, which are then separated during the subsequent sedimentation process, achieving deep oil removal from the aqueous phase. The aqueous phase oil removal process also adopts a physical demulsification method, which has the advantages of high efficiency, energy saving, and environmental protection.

[0030] 5) As oilfields are currently entering a high water-cut phase, the volume of produced fluid is continuously increasing and its properties are complex. The resulting emulsions are highly stable, leading to a series of problems such as increased load and energy consumption for oilfield surface treatment systems. Existing methods for removing suspended solids from produced fluids are ineffective, and the oil-water separation process suffers from problems such as insufficient demulsifier usage and separation depth. Under the residence times of most industrial applications, deep oil-water demulsification and separation cannot be achieved through a single treatment. The device of this invention, through the construction of a compact separation system with functional modules, pre-treats the produced fluid, making the treatment process more efficient and environmentally friendly. The wastewater directly meets the reinjection water standards, effectively reducing the investment cost of produced fluid treatment.

[0031] 6) The device of the present invention couples magnetic fields, electric fields, coalescence fields, etc., and realizes the centralized and deep separation of oil, gas and water through a set of devices. It effectively reduces the water content of the separated oil phase and the oil content in the water phase, while effectively removing solid suspended matter from the oil phase and water phase. The water separation rate reaches more than 90%, and the quality of the effluent can meet the water quality standards for direct reinjection, that is, oil content ≤20mg / L and suspended matter content ≤30mg / L.

[0032] The above description is merely an overview of the technical solution of the present invention. In order to better understand the technical means of the present invention and to implement it according to the contents of the specification, and to make the above and other objects, technical features and advantages of the present invention easier to understand, one or more preferred embodiments are listed below and described in detail with reference to the accompanying drawings. Attached Figure Description

[0033] Figure 1 This is a schematic diagram of the structure of Embodiment 1 of the oilfield produced fluid pretreatment device of the present invention.

[0034] Figure 2 This is a schematic diagram of the structure of Embodiment 2 of the oilfield produced fluid pretreatment device of the present invention.

[0035] Figure 3 This is a schematic diagram of the cross-section of the magnetic separation unit of the present invention.

[0036] Figure 4 This is a schematic diagram of the multi-layer stainless steel grid arrangement of the magnetic separation unit of the present invention.

[0037] Figure 5 This is a schematic diagram of the longitudinal section of the oil phase dehydration subunit in the deep oil-water separation unit of the present invention (showing the direction of oil phase flow).

[0038] Figure 6 This is a cross-sectional schematic diagram of the oil phase dehydration subunit in the deep oil-water separation unit of the present invention (showing the annular electrode plates of each layer and the coalescing packing between the electrode plates).

[0039] Explanation of key figure labels:

[0040] 1-Oilfield produced fluid; 2-Gas-liquid separation unit; 3-Gas phase components; 4-Produced fluid distribution orifice plate; 5-DC power supply; 6-Magnetic separation unit; 61-Aluminum cylinder; 62-Electromagnetic induction coil; 63-Stainless steel grid (63a to 63d are the first to fourth layers of grid respectively); 64-Magnetic outer cylinder; 7-Solid slag outlet; 8-Oil-water separation feed plate; 9-Blocking baffle; 10-Cyclone separator; 11-Overflow weir plate; 12-Feed distribution orifice plate; 13-... 14-Rectifier distributor, 15-AC power supply, 16-Deep oil-water separation unit, 17-First coalescing packing, 18-Second coalescing packing, 19-Third coalescing packing, 20-Oil phase outlet, 21-Purified oil phase, 22-Water tank of the unit, 23-Purified water phase. Detailed Implementation

[0041] The specific embodiments of the present invention will now be described in detail with reference to the accompanying drawings, but it should be understood that the scope of protection of the present invention is not limited to the specific embodiments.

[0042] Unless otherwise expressly stated, throughout the specification and claims, the term "comprising" or its variations such as "including" or "comprises" shall be understood to include the stated elements or components without excluding other elements or other components.

[0043] In this document, for ease of description, spatial relative terms such as “below,” “under,” “down,” “above,” “above,” “upper,” etc., are used to describe the relationship of one element or feature to another element or feature in the accompanying drawings. It should be understood that spatial relative terms are intended to encompass different orientations of an object in use or operation, in addition to those depicted in the figures. For example, if an object in the figure is flipped, an element described as “below” or “under” another element or feature would be oriented “above” that element or feature. Thus, the exemplary term “below” can encompass both the downward and upward orientations. An object may also have other orientations (rotated 90 degrees or other orientations), and the spatial relative terms used herein should be interpreted accordingly.

[0044] In this document, the terms "first," "second," etc., are used to distinguish two different elements or parts, and are not used to define specific positions or relative relationships. In other words, in some embodiments, the terms "first," "second," etc., can also be used interchangeably.

[0045] The oilfield produced fluid pretreatment device of the present invention mainly includes a magnetic separation unit for separating solid suspended matter in the produced fluid and an oil-water deep separation unit for deeply separating the oil phase and water phase in the produced fluid. The device may also include a gas-liquid separation unit, a preliminary oil-water separation unit, and a sedimentation unit after deep oil-water separation. The above units will be described below according to the direction of produced fluid flow.

[0046] Gas-liquid separation unit:

[0047] like Figure 1 , 2 As shown, before entering the gas-liquid separation unit, the produced fluid 1 is heated to 60℃~70℃, and flocculant and magnetic seed are injected and thoroughly mixed. The purpose of injecting flocculant and magnetic seed is to facilitate the subsequent separation of fixed suspended particles. The preferred amount of flocculant and magnetic seed is 0.05~0.1wt% of the produced fluid mass. The preferred amount of magnetic seed is 0.05~0.1wt% of the produced fluid mass. The produced fluid 1 enters the gas-liquid separator 2 tangentially from the inlet pipe. Due to the mass difference between the gas and liquid flows, different centrifugal forces are generated. The liquid phase, with greater centrifugal force, moves towards the wall of the gas-liquid separator 2 and flows out from the lower liquid phase outlet (not shown in the figure), entering the main cavity of the device. The gas phase component 3 moves towards the center of the gas-liquid separator 2 and flows out from the upper gas phase outlet.

[0048] Magnetic separation unit:

[0049] The magnetic separation unit 6 has a cylindrical structure and contains multiple layers of magnetic media. Through the action of a magnetic field, these multiple layers of magnetic media adsorb solid suspended matter encapsulated by flocculants, with magnetic seeds at their core, from the produced fluid. Specifically, the produced fluid after gas-liquid separation enters the magnetic separation unit 6 through the produced fluid distribution orifice plate 4, where solid suspended matter is removed. The magnetic separation unit consists of a magnetic field generating device and an aluminum cylinder 61 fixed to the distribution orifice plate 4 (see [link to documentation]). Figure 3 ). Further as Figure 3 , 4 As shown, the aluminum cylinder 61 contains multiple layers of magnetic focusing medium, which can be stainless steel grating 63. Preferably, but not limitingly, the aluminum cylinder 61 is 800 mm long and 3 mm thick, and the stainless steel grating 63 is made of SUS430 stainless steel. Each layer of grating has parallel stainless steel wires. Preferably, but not limitingly, the stainless steel wires of adjacent layers of grating extend in staggered directions. Figure 4As shown, the included angle α between the extending directions of the stainless steel wires in adjacent layers of the grating is 0–90°, preferably 45°. That is, the stainless steel wires in the first layer 63a are arranged horizontally, the second layer 63b is arranged at a 45° angle, the third layer 63c continues to be arranged at a 45° angle with the stainless steel wires vertically, and so on for the fourth layer 63d. The grating diameter can be 100 mm, and the stainless steel wire diameter can be 0–1 mm, preferably 0.45–0.55 mm; further as… Figure 4 As shown, the wire spacing d is 0–6 mm, preferably 1.5–2.5 mm; the spacing L between adjacent layers of the grid is 0–30 mm, preferably 10–15 mm. Using an alternating arrangement of the stainless steel wires in adjacent grid layers can more effectively adsorb solid suspended particles. The grids are arranged regularly from left to right at a certain angle within the aluminum cylinder 61. When the grid size, arrangement angle, and arrangement interval are within the aforementioned preferred ranges, the interaction between the stainless steel wires is strongest. Stronger interaction can bend the magnetic field lines in the space as much as possible, resulting in a wider distribution of the magnetic field strength on the vertical surface.

[0050] The magnetic field generating device is located outside the aluminum cylinder 61. Due to the presence of the stainless steel grid 63, a high-gradient magnetic field is formed inside the aluminum cylinder 61. This high-gradient magnetic field can adsorb small-diameter solid particles onto the stainless steel grid 63 (i.e., the magnetically focusing medium). The high-gradient magnetic field is achieved by placing a magnetically focusing medium such as steel wool or steel mesh in a uniform magnetic field, so that after being magnetized, a highly non-uniform magnetic field is generated on its radial surface, i.e., a high-gradient magnetization magnetic field. Using this high-gradient non-uniform magnetic field, fine-particle solid suspensions with extremely weak magnetic properties can be separated. Under the action of magnetic seeds and flocculants, the adsorption effect is even better.

[0051] Further as Figures 1 to 3 As shown, the magnetic field generating device consists of a first magnet and a second magnet. The first magnet is disposed on the outer wall of the aluminum cylinder 61 and is used to generate a uniform magnetic field distributed in the vertical direction within the aluminum cylinder 61. This first magnet can be an electromagnetic induction coil 62 wound around the aluminum cylinder 61, and the electromagnetic induction coil 62 is energized with direct current (see [reference]). Figure 1The first magnet is located outside the first magnet and generates a uniform horizontal magnetic field distributed within the aluminum cylinder 61. This second magnet can be an outer magnet cylinder 64, which is an electromagnet made of copper wire wound around a ring-shaped iron core. The electromagnetic induction coil 62 and the outer magnet cylinder 64 form a horizontal and vertical magnetic field with a strength of 0.6T. The electromagnetic induction coil 62 and the outer magnet cylinder 64 are alternately energized and de-energized, switching every 60-180 seconds. The alternating generation of the uniform vertical and horizontal magnetic fields causes the magnetic field strength between the stainless steel grid wires in the aluminum cylinder to alternately increase, achieving uniform adsorption of small-diameter solid suspended particles within the aluminum cylinder 61. The alternating operation of the two magnetic field generating devices, causing the magnetic field strength between the stainless steel grid wires to alternately increase, effectively prevents a large number of particles from directly remaining between the first layer of grids and being unable to continue flowing, thus avoiding premature blockage of the aluminum cylinder 61 before reaching overall adsorption saturation.

[0052] The magnetic separation unit of this invention has a built-in transversely arranged stainless steel grid. The grid is placed in a magnetic field and magnetized, and its surface can generate a high gradient magnetic field. After the solid particles in the extracted fluid are mixed evenly with the magnetic seeds and flocculants, they form flocculent precipitates with the magnetic seeds as the core. During the flow process, they are adsorbed onto the grid, realizing the separation of solid suspended matter and achieving higher separation efficiency.

[0053] Oil-water preliminary separation unit:

[0054] like Figure 1 , 2 As shown, the produced fluid, after being adsorbed and desorbed by the magnetic separation unit 6 (the solid suspended particles fall off and are discharged from the solid slag outlet 7 after the magnetic separation unit 6 is de-energized), enters the oil-water preliminary separation unit from the tangential inlet for oil-water separation. The oil-water preliminary separation unit preferably adopts a hydrocyclone separator 10. Due to the difference in oil and water density, centrifugal forces of different magnitudes are generated. The water phase has a greater centrifugal force and moves towards the wall of the oil-water preliminary separation unit 10, flowing out from the lower water phase outlet, while the oil phase moves towards the center and flows out from the upper oil phase outlet.

[0055] The oil-water preliminary separation unit of the present invention uses a cyclone method to initially separate the oil phase and water phase in the produced fluid, creating more favorable conditions for subsequent targeted treatment of deep dehydration of the oil phase and deep oil removal of the water phase, thereby improving the overall processing effect of the device.

[0056] Oil-water deep separation unit:

[0057] like Figure 1 , 2As shown, the oil-water deep separation unit 15 receives the produced fluid after magnetic separation and preliminary oil-water separation, and performs deep oil-water separation. This unit includes an oil phase dehydration subunit and may also include an aqueous phase oil removal subunit. The oil phase dehydration subunit is equipped with multiple layers of annularly spaced electrode plates and coalescing packing. The oil phase of the produced fluid flows sequentially through the multiple layers of coalescing packing. Under the action of the electric field and the coalescing packing, tiny water droplets in the oil phase can coalesce into larger water droplets. For details, see [link to details]. Figure 1 and Figure 2 After initial oil-water separation, under the isolation effect of the partition baffle 9, the oil phase (which still contains small water droplets) is above the partition baffle 9, and the water phase (which contains oil droplets) is below the partition baffle 9. The partition baffle 9 is connected to the overflow weir plate 11. Under the action of the overflow weir plate 11, the oil phase enters from above and reaches the feed distribution orifice plate 12. The separation cylinder of the oil-water deep separation unit 15 of the present invention is fixed on the feed distribution orifice plate 12. This separation cylinder is the oil phase dehydration subunit, and multiple units can be set and arranged horizontally, such as... Figure 5 , 6 As shown, the separation cylinder consists of three layers of annularly spaced electrode plates and coalescing filler. The electrode plates include a first electrode plate 154, a second electrode plate 155, and a third electrode plate 156. The first electrode plate 154 is annular and located on the outermost layer. The second electrode plate 155 is also annular and located inside the first electrode plate 154. A first cavity is provided between the first electrode plate 154 and the second electrode plate 155, and this first cavity is filled with first coalescing filler 151. The third electrode plate 156 is also annular and located inside the second electrode plate 155. A second cavity is provided between the second electrode plate 155 and the third electrode plate 156, and this second cavity is filled with second coalescing filler 152. The interior of the third electrode plate 156 is a third cavity, which is filled with third coalescing filler 153. Alternating current (i.e., AC power supply 14) is applied between the electrode plates. Specifically, the first electrode plate 154 and the third electrode plate 156 are grounded, and the second electrode plate 155 is connected to the live wire of the power supply. After energization, the electric field strength in the first cavity is 350–450 V / cm; the electric field strength in the second cavity is 800–1500 V / cm. The oil phase channels between the annular electrode plates (i.e., the three cavities) are filled with coalescing filler, with the filler precision increasing sequentially from the outermost layer to the innermost layer. The coalescing filler is woven from a 3:1 mixture of hydrophilic and oleophobic polypropylene fibers. The oil phase enters through the inlet, flows sequentially through the three cavities, and exits through the outlet of the innermost channel (i.e., the third cavity).

[0058] It should be noted that the oil-water deep separation unit of the present invention can be configured in various ways, such as the present invention. Figure 1 Example 1 and shown in the figure Figure 2 Example 2 is shown in the figure.

[0059] Example 1 uses a fluid flow pattern in both the shell side and the tube side, specifically, the oil phase flows in the oil phase dehydration subunit (equivalent to the tube side). See [link to example]. Figure 1 The blank area indicated by the middle arrow, outside the oil phase dehydration subunit, corresponds to the shell side, i.e., the aqueous phase dehydration subunit, which is filled with structured fiber packing 17. The aqueous phase below enters the aqueous phase dehydration subunit through the rectifier distributor 13. Since the aqueous phase flows along the shell side, it can enter the upper structured fiber packing 17. Each layer of structured fiber packing 17 can be filled in a multi-stage stacked manner. Each stage of structured fiber packing is woven from a 4:1 mixture of oleophilic and hydrophobic polypropylene fibers and hydrophilic and oleophobic polypropylene fibers. The surface of each fiber layer can have an X-shaped structure with concave and convex features, and the packing precision increases sequentially along the fluid flow direction. A packing baffle 16 can also be installed between the packings to increase the travel distance of the oil phase during flow, thereby improving the water droplet accumulation efficiency. The method described in Example 1 can enhance the oil phase dehydration effect.

[0060] In Example 2, an average partitioning method was used to perform oil phase dehydration and aqueous phase oil removal separately. See [link to example]. Figure 2 That is, the partition baffle 9 runs longitudinally through the entire oil-water deep separation unit, with the upper part being the oil phase dehydration subunit and the lower part being the water phase oil removal subunit. The arrangement of the electrode plates and coalescing packing in the subunit is the same as in Example 1, and will not be repeated here. Using the method of Example 2 can enhance the effect of water phase oil removal.

[0061] The deep oil-water separation unit of this invention utilizes an electric field to drive the rapid migration of tiny water droplets. By leveraging media interception and wetting coalescing, it provides a wide range of media sites for droplet coalescing, solving the problem of low droplet collision interception efficiency in electric field coalescing. Through the combined action of the electric field and the coalescing field, tiny water droplets more easily coalesce into larger droplets, which are then separated during subsequent settling, achieving deep dehydration of the oil phase. The aqueous phase oil removal employs a structured fiber packing coalescing method. The coalescing packing is arranged in a graded manner and assembled from a mixture of oleophilic and hydrophobic fibers woven into a specific structure. Small oil droplets in the produced fluid entering the packing are more easily coalesced into larger droplets, which are then separated during subsequent settling, achieving deep oil removal of the aqueous phase. All of the above processes utilize physical demulsification, offering advantages such as high efficiency, energy saving, and environmental friendliness.

[0062] Settlement unit:

[0063] The settling unit is located at the rear end of the oil-water deep separation unit 15 and is used to separate the produced fluid after oil phase dehydration and water phase oil removal treatment by settling. After dehydration, the oil phase flows out from the discharge orifice plate 18. The settling unit is equipped with a vertically arranged settling baffle 19. The purified oil phase 21 after deep separation flows out from the oil phase outlet 20 at the top of the settling unit, and the purified water phase 23 after deep separation flows out from the water tank 22 of the device, realizing the settling separation of the purified oil phase and water phase after deep separation.

[0064] The foregoing description of specific exemplary embodiments of the present invention is for illustrative and explanatory purposes. These descriptions are not intended to limit the invention to the precise forms disclosed, and it will be apparent that many changes and variations can be made in accordance with the foregoing teachings. The exemplary embodiments were chosen and described in order to explain the specific principles of the invention and its practical application, thereby enabling those skilled in the art to implement and utilize various different exemplary embodiments of the invention, as well as various different choices and variations. Any simple modifications, equivalent changes, and alterations made to the foregoing exemplary embodiments should fall within the scope of protection of the present invention.

Claims

1. An oilfield produced fluid pretreatment device, characterized in that, include: The magnetic separation unit is a cylindrical structure with multiple layers of magnetically concentrated media inside. Under the action of a magnetic field, these multiple layers of magnetically concentrated media adsorb solid suspended matter in the produced fluid. The magnetic separation unit receives the produced fluid after heating and injection of flocculant and magnetic seeds. A high-gradient magnetic field is formed inside the cylindrical structure by a magnetic field generator outside the cylindrical structure. Under the action of this high-gradient magnetic field, the magnetically concentrated media adsorbs flocculent precipitates with the magnetic seeds as the core. The cylindrical structure is an aluminum cylinder, and the magnetically concentrated media is a stainless steel grid. The stainless steel wires of adjacent grid layers extend in staggered directions. An oil-water deep separation unit receives the produced fluid after magnetic separation and preliminary oil-water separation, and performs deep oil-water separation; the oil-water deep separation unit includes an oil phase dehydration subunit, which is provided with multiple layers of annularly spaced electrode plates and coalescing packing; the multiple layers of annularly spaced electrode plates include: a first electrode plate, which is arranged in annularly and located on the outermost layer. The second electrode plate is arranged in a ring and located inside the first electrode plate. A first cavity is provided between the first and second electrode plates, and the first cavity is filled with a first coalescing filler. The third electrode plate is arranged in a ring and located inside the second electrode plate. A second cavity is provided between the second and third electrode plates, and the second cavity is filled with a second coalescing filler. The interior of the third electrode plate is a third cavity, which is filled with a third coalescing filler. The oil phase of the produced fluid flows sequentially through multiple layers of the coalescing filler. Under the action of the electric field and the coalescing filler, the tiny water droplets in the oil phase coalesce into larger water droplets.

2. The oilfield produced fluid pretreatment device according to claim 1, characterized in that, An alternating current is applied between the first electrode plate, the second electrode plate, and the third electrode plate; the electric field strength in the first cavity is 350–450 V / cm; and the electric field strength in the second cavity is 800–1500 V / cm.

3. The oilfield produced fluid pretreatment device according to claim 1, characterized in that, The first coalescing filler, the second coalescing filler and the third coalescing filler are woven from a mixture of hydrophilic and oleophobic polypropylene fibers in a 3:1 ratio.

4. The oilfield produced fluid pretreatment device according to claim 1, characterized in that, The deep oil-water separation unit also includes an aqueous phase oil removal subunit. In this aqueous phase oil removal subunit, a multi-stage structured fiber packing is arranged along the direction of water phase flow. The structured fiber packing is woven from a mixture of oleophilic and hydrophobic polypropylene fibers and hydrophilic and oleophobic polypropylene fibers in a 4:1 ratio.

5. The oilfield produced fluid pretreatment device according to claim 1, characterized in that, The diameter of the stainless steel wires in the grille is 0.45 to 0.55 mm; the spacing between the stainless steel wires is 1.5 to 2.5 mm; and the spacing between adjacent layers of the grille is 10 to 15 mm.

6. The oilfield produced fluid pretreatment device according to claim 5, characterized in that, The included angle of the extension direction of the stainless steel wire is 0 to 90°, and the included angle is not zero.

7. The oilfield produced fluid pretreatment device according to claim 6, characterized in that, The magnetic field generating device includes: A first magnet is disposed on the outer wall surface of the aluminum cylinder to generate a uniform magnetic field distributed in the vertical direction within the aluminum cylinder. A second magnet, disposed outside the first magnet, is used to generate a uniform magnetic field distributed in the horizontal direction within the aluminum cylinder.

8. The oilfield produced fluid pretreatment device according to claim 7, characterized in that, The first magnet is an electromagnetic induction coil wound around the outer wall of the aluminum cylinder; the second magnet is a magnetic outer cylinder composed of electromagnets; the uniform magnetic field in the vertical direction and the uniform magnetic field in the horizontal direction are generated alternately to drive the flocculent precipitate with magnetic seeds as the core to be uniformly adsorbed on each layer of the grid.

9. The oilfield produced fluid pretreatment device according to claim 8, characterized in that, The outer cylinder of the magnet is made of a ring-shaped iron core wound with copper wire.

10. The oilfield produced fluid pretreatment device according to claim 8, characterized in that, The magnetic field strength of the vertical and horizontal uniform magnetic fields is 0.6T, and the alternation time between the two is 60 to 180 seconds.

11. The oilfield produced fluid pretreatment device according to claim 1, characterized in that, The oilfield produced fluid pretreatment device also includes: A gas-liquid separation unit is located at the front end of the magnetic separation unit. The extracted liquid enters the wall of the gas-liquid separation unit tangentially, and the extracted liquid is separated into gas and liquid by the difference in centrifugal force between gas and liquid.

12. The oilfield produced fluid pretreatment device according to claim 1, characterized in that, The oilfield produced fluid pretreatment device also includes: The oil-water preliminary separation unit is located between the magnetic separation unit and the oil-water deep separation unit. It performs preliminary separation of oil and water by using swirling current and the difference in oil and water density.

13. The oilfield produced fluid pretreatment device according to claim 4, characterized in that, The oilfield produced fluid pretreatment device also includes: A sedimentation unit, located at the rear end of the oil-water deep separation unit, is used to separate the produced fluid after oil phase dehydration and water phase oil removal treatment by sedimentation.

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