Efficient treatment and sludge concentration device for fracturing flowback fluid

Abstract

The application provides a high-efficiency treatment and sludge concentration device for fracturing flowback fluid, which comprises an electric flocculator, a settling cylinder and a cyclone pipe. The electric flocculator comprises a plurality of flocculation tubes arranged side by side and connected in series, a U-shaped joint connected between adjacent flocculation tubes, and a power supply for supplying power to the flocculation tubes. The settling cylinder is used for separating oil, water and mud in the fracturing flowback fluid. The cyclone pipe is connected to the outlet end of the electric flocculator and extends into the settling cylinder along the tangent direction of the cross section of the settling cylinder. The electric flocculator and the settling cylinder are arranged. The electric flocculator breaks the emulsification of the fracturing flowback fluid, and flocculates the oil droplets, suspended impurities and solid impurities in the fracturing flowback fluid into flocs, so that the oil, water and mud can be separated by the subsequent settling cylinder.

Description

Technical Field

[0001] This invention belongs to the field of oilfield wastewater treatment technology. Specifically, it relates to a high-efficiency treatment and sludge thickening device suitable for fracturing flowback fluid, wellhead spray fluid, well washing, and operational wastewater. It can also be used for the treatment of produced water from conventional oil and gas fields with high emulsification, many solid impurities, and limited space. Background Technology

[0002] With the increasing maturity of fracture network fracturing, volumetric fracturing, horizontal well cross-layer fracturing, and horizontal well multi-stage fracturing technologies, low-permeability unconventional oil and gas reserves, represented by tight oil and gas and shale oil and gas, are gradually being developed on a large scale. However, this extraction process also generates a large amount of fracturing flowback fluid.

[0003] Fracturing flowback fluid contains more than a dozen chemical additives such as thickeners and crosslinking agents, giving it a strong sand-carrying capacity. However, due to the presence of these additives, fracturing flowback fluid is characterized by high viscosity, high emulsification, high content of large-particle mechanical impurities, high TDS (total dissolved solids) content, difficulty in oil-water sedimentation and separation, and large fluctuations in water quality.

[0004] Currently, there are two main methods for treating fracturing flowback fluid. One method is to reinject the flowback fluid into the formation. However, this method has high requirements for the selection of the reinjection formation, and the remaining reinjection space is decreasing year by year, making it unsuitable for large-scale injection and posing high environmental risks. The other method is to transport large quantities of fracturing flowback fluid to a combined treatment station for centralized processing via tanker trucks. However, if a large amount of fracturing flowback fluid directly enters the combined treatment station, it will seriously disrupt the normal operation of the production system, consume a large amount of treatment agents or reduce the effectiveness of the agents, and affect crude oil dehydration and the removal of oil and suspended solids from the water, thus resulting in substandard injected water quality. Therefore, before entering the combined treatment station system, fracturing flowback fluid generally needs to undergo pretreatment, such as magnetic separation, SSF suspended sludge treatment, and biochemical treatment, to remove solid impurities, suspended solids, and colloids from the fracturing flowback fluid and reduce the turbidity of the water sample. These methods each have their own advantages and disadvantages. Magnetic separation requires a large amount of magnetic powder, which is difficult to recover, resulting in high processing costs and the generation of large amounts of hazardous sludge. SSF suspended sludge treatment technology has poor resistance to water quality fluctuations and still requires the addition of flocculants and coagulants to form flocs, making it difficult to control the sludge layer effect. Fracturing flowback fluid has poor biodegradability, large water quality fluctuations, and microorganisms have difficulty surviving in winter. In addition, the dispersed production well areas of tight oil and gas and shale oil and gas, the distribution of environmental protection reservoirs, and insufficient storage space pose a risk of leakage.

[0005] Therefore, the development of fracturing flowback fluid skid-mounted treatment technology to quickly capture impurities, achieve rapid floc separation, purify water, and concentrate sludge for on-site recycling and reinjection is a technological trend. Summary of the Invention

[0006] To address the technical problems mentioned above, this invention aims to provide a highly efficient treatment and sludge thickening device for fracturing flowback fluid, which is applicable to the demulsification, oil removal, and purification of difficult-to-separate oilfield operation wastewater such as fracturing flowback fluid, wellhead dispensing fluid, and well washing fluid with high emulsification and many solid impurities.

[0007] In addition, this invention features closed-loop oxygen isolation, high efficiency and continuous operation, no or minimal chemical addition, low operating cost, small device size, and easy skid-mounting. It can be used for the treatment of wastewater from ordinary oil and gas fields with high solid impurities, limited space, and high water quality requirements. It is particularly suitable for short-process, high-efficiency treatment of conventional wastewater from oil and gas fields with many emulsified oil droplets and solid impurities.

[0008] According to the present invention, a high-efficiency treatment and sludge thickening device for fracturing flowback fluid is provided, characterized in that it comprises: an electrocoagulant, which utilizes electrodes to demulsify the fracturing flowback fluid and generate electrocoagulation products (polynuclear polymeric hydroxides), i.e., reacting with oil droplets, suspended impurities, and solid impurities in the wastewater to form flocs. The electrocoagulant includes multiple flocculation tubes arranged in parallel and connected in series, a U-shaped connector connecting adjacent flocculation tubes, and a power supply for supplying power to the flocculation tubes; a settling tank, which separates oil, water, and sludge from the fracturing flowback fluid, with the separated sludge deposited and concentrated at the bottom of the settling tank; and a cyclone tube connected to the outlet end of the electrocoagulant, extending tangentially into the settling tank along its cross-section.

[0009] In one specific embodiment, an insulating flange is provided between the flocculation pipe and the U-shaped joint. The flocculation pipe includes a hollow tube connected to the cathode of the power source and a rod-shaped anode connected to the anode of the power source. The hollow tube is an electrical conductor, and the rod-shaped anode is intermittently sleeved inside the hollow tube.

[0010] In one specific embodiment, the high-efficiency treatment and sludge thickening device for fracturing flowback fluid further includes a return water pipe extending from the settling cylinder, a dissolved air water release pipe extending into the settling cylinder, and a microbubble generator connecting the return water pipe and the dissolved air water release pipe. The microbubble generator can generate a large number of micro-nano-sized bubbles. The dissolved air water release pipe is arranged along the tangential direction of the cross-section of the settling cylinder and is used to transport the dissolved air water mixed with a large number of bubbles generated by the microbubble generator into the settling cylinder.

[0011] In one specific embodiment, the return water pipe is below the vortex tube, the dissolved air water release pipe is above the vortex tube, the microbubble generator is connected to the top of the settling cylinder through the return air pipe, and the return water pipe is connected to the microbubble generator through the return water pump.

[0012] In one specific embodiment, a first conical sludge hopper is provided inside the settling cylinder. The first conical sludge hopper is located below the return water pipe, dividing the settling cylinder into a vortex chamber and a sludge collection chamber. A sludge collection port is provided at the lower end of the first conical sludge hopper to connect the vortex chamber and the sludge collection chamber. A sludge discharge port is provided at the bottom end of the sludge collection chamber.

[0013] In one specific embodiment, a vortex generator is also provided inside the settling cylinder. The vortex generator is located below the cyclone tube and directly above the sludge collection port, and can block the transmission of the cyclone intensity in the cyclone chamber to the sludge collection chamber.

[0014] In one specific embodiment, a conical vortex separator is further provided inside the settling cylinder, wherein the inner diameter of the upper end of the conical vortex separator is smaller than the inner diameter of the lower end.

[0015] In one specific embodiment, a second conical sludge bucket is provided at the top of the conical cyclone separator. The upper diameter of the second conical sludge bucket is equal to the diameter of the settling cylinder, and the lower diameter of the second conical sludge bucket is equal to the top diameter of the conical cyclone separator.

[0016] In one specific embodiment, a conical baffle is provided on the central axis of the settling cylinder. The conical baffle is located above the second conical sludge hopper. The upper diameter of the conical baffle is larger than the top diameter of the conical cyclone separator. A sludge pipe is provided between the bottom end of the conical baffle and the sludge collection bin.

[0017] In one specific embodiment, a baffle tube is provided above the conical baffle, the upper diameter of the baffle tube is equal to the diameter of the settling tube, and the lower diameter of the baffle tube is smaller than the upper diameter of the conical baffle.

[0018] In one specific embodiment, a conical wide-mouth oil-water separator is disposed above the baffle cylinder. An oil drain outlet and a water drain outlet are disposed on the outer shell of the settling tank outside the conical wide-mouth oil-water separator. The oil drain outlet is located above the water drain outlet, and the oil drain outlet and the water drain outlet are respectively disposed at the radial ends of the settling tank. By separating the oil drain outlet and the water drain outlet, it is possible to prevent the water flow from carrying separated oil droplets out of the outlet, thus avoiding a deterioration in the quality of the effluent.

[0019] In one specific embodiment, an oil collecting trough is provided inside the settling cylinder, the oil collecting trough is fastened to the oil drain port, and an opening is provided at the top of the oil collecting trough. The presence of the oil collecting trough can ensure liquid level control and prevent the liquid level from impacting the top of the settling cylinder and flowing into the return gas pipe.

[0020] In one specific embodiment, the oil outlet is located above the conical wide-mouth oil-water separator, and the drain outlet is located at the lower part of the settling tank corresponding to the conical wide-mouth oil-water separator. The purified water flows around the conical wide-mouth oil-water separator and exits the device from the outlet. Oil floats to the surface and accumulates, overflowing into the oil collection tank and exiting the device from the outlet. The wide opening of the conical wide-mouth oil-water separator, i.e., the upper diameter of the conical wide-mouth oil-water separator is larger than the minimum diameter of the baffle, serves to prevent excessive water flow velocity and avoid water impacting the oil layer at the top, thereby reducing the amount of oil droplets carried by the water flow.

[0021] Compared with the prior art, the advantages of this application are as follows.

[0022] This invention incorporates an electrocoagulant and a settling tank. The electrocoagulant uses electrodes to demulsify the severely emulsified fracturing flowback fluid, causing oil droplets, suspended impurities, and solid impurities in the flowback fluid to coagulate into flocs, facilitating the subsequent separation of oil, water, and mud in the settling tank.

[0023] Furthermore, the electrocoagulant of the present invention includes multiple flocculation tubes arranged side by side, and adjacent flocculation tubes are connected by U-shaped joints. The fracturing flowback fluid flows along the tortuous pipeline, which on the one hand strengthens the collision between fluids and accelerates flocculation; on the other hand, some flocs stay briefly at the U-shaped joints, which helps to prolong the flocculation time and improve the flocculation effect.

[0024] In addition, the flocculation tube of the present invention includes a hollow tube connected to the cathode of the power supply and a rod-shaped anode connected to the anode of the power supply. It makes full use of the annular space inside the flocculation tube so that the fracturing flowback fluid can be subjected to the action of the cathode and anode throughout the entire process of flowing through the flocculation tube, thereby enhancing the flocculation and demulsification effects.

[0025] Meanwhile, the settling cylinder of the present invention is also equipped with a first conical mud hopper, a conical cyclone separator, a microbubble generator, etc., which can enhance the separation effect of oil, water and mud and improve work efficiency. Attached Figure Description

[0026] The present invention will now be described with reference to the accompanying drawings.

[0027] Figure 1 A schematic diagram of an embodiment of a fracturing flowback fluid treatment and sludge thickening device according to the present invention is shown.

[0028] Figure 2 A schematic diagram of the oil collection tank according to the present invention is shown.

[0029] In the diagram: 1. Electrocoagulant; 10. Inlet pipe; 11. Flocculation pipe; 111. Hollow pipe; 112. Rod anode; 12. U-joint; 13. Power supply; 14. Insulating flange; 15. Anode wiring hole; 16. Anode conductor; 17. Cathode connector; 18. Cathode conductor; 2. Settling cylinder; 21. First conical sludge hopper; 211. Sludge collection port; 22. Cyclone chamber; 23. Sludge collection chamber; 231. Sludge discharge port; 24. Vortex generator 25. Conical cyclone separator; 26. Second conical sludge hopper; 3. Cyclone tube; 5. Conical baffle; 6. Sludge tube; 7. Baffle tube; 81. Return water pump; 82. Microbubble generator; 83. Dissolved gas water release pipe; 84. Return gas pipe; 85. Return water pipe; 9. Liquid level; 91. Oil outlet; 92. Drain outlet; 93. Conical wide-mouth oil-water separator; 95. Oil collection tank; 100. High-efficiency treatment and sludge thickening device.

[0030] In this application, all drawings are schematic and are used only to illustrate the principles of the invention, and are not drawn to scale. Detailed Implementation

[0031] The invention will now be described with reference to the accompanying drawings.

[0032] In this application, it should be noted that the directional terms or qualifiers such as "up" and "down" used herein are all specific to the referenced material. Figure 1 In other words, they are not used to define the absolute position of the components involved, but can vary depending on the specific circumstances.

[0033] Figure 1 A schematic diagram of one embodiment of a fracturing flowback fluid high-efficiency treatment and sludge thickening device 100 according to the present invention is shown. Figure 1As shown, the high-efficiency treatment and sludge thickening device 100 for fracturing flowback fluid includes an electrocoagulant 1, a hollow cylindrical settling tank 2, and a cyclone separator 3. An inlet pipe 10 is provided at the inlet of the electrocoagulant 1. The cyclone separator 3 is arranged tangentially to the cross-section of the settling tank 2, connecting the outlet of the electrocoagulant 1 and the inlet of the settling tank 2. In this configuration, the fracturing flowback fluid enters the electrocoagulant 1 through the inlet pipe 10. The electrocoagulant 1 demulsifies the severely emulsified fluid, facilitating oil-water separation. Furthermore, the electrocoagulant 1 coagulates some suspended impurities and solid impurities in the fracturing flowback fluid into flocs, which serve as part of the sludge in subsequent treatment. The flocs also adhere to some oil droplets in the fracturing flowback fluid, facilitating the separation of oil droplets from the water. After preliminary treatment by the electrocoagulant 1, the fracturing flowback fluid passes through the cyclone separator 3 and enters the settling tank 2. Because the cyclone tube 3 is arranged tangentially to the cross-section of the settling cylinder 2, the fracturing flowback fluid will generate a vortex after entering the settling cylinder 2. Under the action of centrifugal force, oil, water, and mud are further separated. Furthermore, under continuous collision, tiny oil droplets gradually form larger oil droplets, which is beneficial for oil-water separation. With this configuration of the present invention, the separation of oil, water, and mud can be completed without adding (or with minimal addition) chemicals.

[0034] In a preferred embodiment, the electrocoagulant 1 includes a power supply 13 and multiple flocculation pipes 11 connected to the power supply 13. The multiple flocculation pipes 11 are arranged side by side and connected in series. In this embodiment, all the multiple flocculation pipes 11 are arranged horizontally. The horizontal placement of the flocculation pipes 11 can increase the contact time between the fracturing flowback fluid and the electrocoagulation products, which is conducive to the formation, aggregation and growth of flocs. Adjacent flocculation pipes 11 are connected by U-shaped joints 12 to form a bent pipeline. Through this arrangement, on the one hand, the overall size of the electrocoagulant 1 is reduced; on the other hand, the turbulence effect of the bend is conducive to the formation, aggregation and growth of flocs. At this time, most of the oil droplets and suspended impurities in the fracturing flowback fluid are separated without the addition of chemicals.

[0035] In a preferred embodiment, the flocculation tube 11 includes a hollow tube 111 and a rod-shaped anode 112. An insulating flange 14 is provided between the hollow tube 111 and the U-shaped connector 12 to separate multiple flocculation tubes. The insulating flange 14 ensures that the electroflocculation reactions within the series-connected flocculation tubes 11 do not affect each other, thus ensuring the flocculation effect. The hollow tube 111 is connected to the cathode of the power supply 13, and the hollow tube 111 is an electrical conductor, serving as the cathode of the electric field. The rod-shaped anode 112 is intermittently sleeved inside the hollow tube 111 and connected to the anode of the power supply, serving as the anode of the electric field. In this configuration, the anode and cathode can occupy the entire length of the flocculation tube 11. This increases the time that the fracturing flowback fluid is subjected to the electric field and flocculation effect when flowing in the flocculation tube 11 at the same flow rate. At the same time, the rod-shaped anode and the tubular cathode work together to increase the contact area between the fracturing flowback fluid and the anode and cathode. In this way, the flocculation and demulsification effects are enhanced in multiple ways.

[0036] In one specific embodiment, the rod-shaped anode 112 is fixedly connected to the hollow tube 111 via an insulating component (not shown in the figure), thereby achieving the purpose of intermittently fitting inside the hollow tube 111. At the same time, in order to allow the fracturing flowback fluid to flow, this insulating component must not block the hollow tube 111; for example, it can be fixed by a quincunx-shaped hard rubber or plastic.

[0037] In one specific embodiment, an anode connection hole 15 is provided on the wall of the hollow tube 111, and a rod-shaped anode 112 is connected to the power supply 13 through the anode connection hole 15 via an anode wire 16. A cathode connection piece 17 is provided on the wall of the hollow tube 111, and the cathode connection piece 17 is connected to the power supply 13 via a cathode wire 18, thereby making the entire hollow tube 111 serve as a cathode.

[0038] According to the present invention, a first conical sludge hopper 21 is provided inside the settling cylinder 2, which divides the settling cylinder 2 into a lower sludge collection chamber 23 and an upper cyclone chamber 22. The first conical sludge hopper 21 is located below the cyclone pipe 3, meaning that the fracturing flowback fluid flowing out of the cyclone pipe 3 can enter the cyclone chamber 22. After entering the cyclone chamber 22, the fracturing flowback fluid forms a vortex, rotating and colliding within the cyclone chamber 22. Under the action of centrifugal force, the separation speed of mud, water, and oil is accelerated. At the same time, the fracturing flowback fluid continuously collides with each other, causing small oil droplets to collide and condense into large oil droplets, which is beneficial to oil-water separation. A sludge collection port 211 is provided at the lower end of the first conical sludge hopper 21, which connects the cyclone chamber 22 and the sludge collection chamber 23. With this setup, under the action of the first conical sludge hopper 21, the swirling intensity within the cyclone chamber 22 has little impact on the sludge collection chamber 23. Therefore, the mud-water mixture separated by the cyclone chamber 22 enters the sludge collection chamber 23 through the sludge collection port 211 and begins to concentrate and settle. As the amount of mud in the sediment increases, the water is gradually squeezed to the top and returns to the cyclone chamber 22. The sludge accumulates and concentrates, reducing its water content and lowering subsequent transportation and treatment costs. A sludge discharge port 231 is provided at the bottom of the sludge collection chamber 23. The opening and closing time of the sludge discharge port 231 is adjusted according to the sedimentation rate of the mud in the sludge collection chamber 23, and the mud is discharged through the sludge discharge port 231. If the amount of mud is large, the mud-water separation and sludge concentration are carried out continuously before sludge discharge; if the amount of mud is small, the sludge is discharged intermittently, allowing the sludge to accumulate and concentrate more, reducing its water content.

[0039] According to a specific embodiment of the present invention, a vortex generator 24 is further provided inside the settling cylinder 2. The vortex generator 24 is located directly above the mud collection port 211, and the outer diameter of the vortex generator 24 is larger than the diameter of the mud collection port 211. In this embodiment, the vortex generator 24 is a cone shape that is narrower at the top and wider at the bottom. With this arrangement, on the one hand, the vortex generator 24 can enhance the swirling intensity. On the other hand, the vortex generator 24 can further reduce the influence of the swirling intensity in the swirling chamber 22 on the mud collection chamber 23, preventing the mud settled in the mud collection chamber 23 from being rolled back into the swirling chamber 22.

[0040] In one specific embodiment, a conical cyclone separator 25 is also provided inside the settling cylinder 2, located above the cyclone tube 3. The upper diameter of the conical cyclone separator 25 is larger than the lower diameter. With this arrangement, the collisions inside the fracturing flowback fluid are more intense under the gradually decreasing cylinder diameter, accelerating the collisions between oil droplets and causing small oil droplets to coalesce into large oil droplets, which is beneficial for oil-water separation.

[0041] In one specific embodiment, a second conical sludge hopper 26 is provided at the top of the conical cyclone separator 25. The upper diameter of the second conical sludge hopper 26 is equal to the diameter of the settling cylinder 2, and the lower diameter of the second conical sludge hopper 26 is equal to the diameter of the upper end of the conical cyclone separator 25. This arrangement allows any remaining small amount of sludge in the fracturing flowback fluid above the conical cyclone separator 25 to settle onto the second conical sludge hopper 26 and slide down along the conical surface, preventing sludge accumulation there.

[0042] In a preferred embodiment, a conical baffle 5 is provided above the second conical sludge hopper 26. The upper diameter of the conical baffle 5 is larger than the diameter of the top of the conical cyclone separator 25, but smaller than the inner diameter of the settling cylinder 2. This arrangement abruptly reduces the flow path of the fracturing flowback fluid, which facilitates faster impact of the fracturing flowback fluid against the conical baffle 5, accelerating the settling of solid particles and the coalescence of oil droplets. To prevent sludge accumulation above the conical baffle 5, a sludge pipe 6 is connected to the bottom end of the conical baffle 5, and the bottom end of the sludge pipe 6 connects to the sludge collection bin 23. The sludge pipe 6 can be configured as follows: Figure 1 As shown, the tube extends out of the settling cylinder 2 and connects to the sludge collection bin 23 from the outside. Alternatively, it can connect to the sludge collection bin 23 along the inner wall of the settling cylinder 2 without affecting the internal flow field of the conical cyclone separator 25. In this configuration, if solid particles accumulate above the conical baffle 5, the accumulated solid particles will move to the sludge collection bin 23 along the sludge sliding pipe 6.

[0043] In a preferred embodiment, a baffle 7 is provided above the conical baffle 5. The upper diameter of the baffle 7 is equal to the diameter of the settling tank 2, and the lower diameter of the baffle 7 is smaller than the upper diameter of the conical baffle 5. A narrow channel for flow deflection is formed between the baffle 7 and the conical baffle 5. Through the baffle channel, oil droplet aggregation can be further enhanced, allowing it to separate from the wastewater; the remaining solid particles, during their flow within the narrow channel, impact the conical baffle 5 due to inertia, settle on the conical baffle 5, and then flow along the sludge pipe 6 to the sludge collection bin 23. Simultaneously, this arrangement reduces the influence of the swirling intensity at the lower part of the baffle 7 on the upper part, facilitating oil-water stratification at the upper part. According to a specific embodiment of the present invention, an oil drain 91 and a water drain 92 are provided on the upper wall of the settling tank 2. The oil drain 91 is located above the water drain 92, and the oil drain 91 and water drain 92 are respectively located at the radial ends of the settling tank 2. Figure 1 As shown in the diagram, in this embodiment, the drain outlet 92 is located on the left side of the settling cylinder 2, and the oil outlet 91 is located on the right side of the settling cylinder 2. By staggering the drain outlet 92 and the oil outlet 91 to increase the distance between them, it is possible to prevent the water flow from carrying away the separated oil droplets and flowing out of the outlet, thus avoiding a deterioration in the quality of the effluent.

[0044] Combination Figure 1 and Figure 2 An oil collecting trough 95 is provided inside the settling cylinder 2. In this embodiment, the oil collecting trough 95 is a square shell that fits onto the oil drain port, and an opening is provided at the top of the oil collecting trough 95. The size and shape of the oil collecting trough 95 can be changed according to actual usage requirements. The presence of the oil collecting trough 95 facilitates liquid level control.

[0045] like Figure 1 As shown, a conical wide-mouth oil-water separator 93 is installed above the baffle 7. The oil outlet 91 is located above the conical wide-mouth oil-water separator 93, and the drain outlet 92 is located at the lower part of the corresponding conical wide-mouth oil-water separator 93 in the settling tank 2. The purified water flows around the conical wide-mouth oil-water separator 93 and exits from the outlet 92. Oil floats to the surface and overflows into the oil collection tank 95, exiting the device from the oil outlet 91. By installing the conical wide-mouth oil-water separator 93, oil is prevented from passing through the outlet 92, thus reducing the possibility of the outlet 92 being contaminated by oil. Specifically, the diameter of the top outlet of the conical wide-mouth oil-water separator 93 is larger than the minimum diameter of the baffle 7. This design, which maximizes the outlet diameter of the conical wide-mouth oil-water separator 93, prevents the water flow from impacting the oil layer at the top due to excessive velocity, thus providing a stable environment for oil-water stratification.

[0046] In the actual process of draining and discharging oil, an electric switching valve and an electric regulating valve can be installed on the pipelines of oil outlet 91 and drain outlet 92, respectively. An oil-water interface meter is installed in the settling tank 2. The oil-water interface meter can detect the liquid level of oil and water. Both the electric switching valve and the electric regulating valve are electrically interlocked with the oil-water interface meter through corresponding circuit components. By controlling the electric switching valve and the electric regulating valve through the oil-water interface meter, the purpose of intelligent draining and discharging oil can be achieved.

[0047] According to a preferred embodiment of the present invention, the high-efficiency treatment and sludge thickening device 100 for fracturing flowback fluid further includes a return water pump 81, a return water pipe 85, a return air pipe 84, a microbubble generator 82, and a dissolved air water release pipe 83. The microbubble generator 82 includes an inlet, an outlet, and an air inlet. The dissolved air water release pipe 83 is arranged tangentially to the cross-section of the settling cylinder 2, consistent with the direction of the cyclone tube 3. The outlet of the microbubble generator 82 is connected to the settling cylinder 2 via the dissolved air water release pipe 83. The return water pump 81 is connected to the inlet of the microbubble generator 82, providing power to the microbubble generator 82. The microbubble generator 82 releases bubbles into the settling cylinder 2 through the dissolved air water release pipe 83. The released bubbles, along with the fracturing flowback fluid ejected from the cyclone tube 3, swirl and mix within the settling cylinder 2, thereby promoting the separation of oil, water, and flocculent matter. In this embodiment, the microbubble generator 82 can generate bubbles with a diameter of 50μm to 90μm, while the small oil droplets in the fracturing flowback fluid have a diameter of 25μm to 70μm. The bubbles can carry the small oil droplets to the top of the water surface quickly, accelerating oil-water separation. A large number of bubbles are released into the settling tank 2 through the tangential dissolved air release pipe 83. Utilizing the geometrically contracted shape of the conical cyclone separator 25, these bubbles, together with the fracturing flowback fluid entering the settling tank 2, create a swirling flotation effect, enhancing the separation of remaining fine oil droplets and suspended impurities. In a preferred embodiment, a return water pipe 85 is provided between the return water pump 81 and the cyclone chamber 22. A return air pipe 84 is provided between the air inlet of the microbubble generator 82 and the top of the settling tank 2. An air cavity exists at the top of the settling tank 2, meaning the fracturing flowback fluid in the settling tank 2 is not completely filled. The return water pipe 85 is below the cyclone tube 3, and the dissolved air release pipe 83 is above the cyclone tube 3. In this setup, the return water pump 81 pumps the fracturing flowback fluid from the cyclone chamber 22 into the microbubble generator 82. The gas in the gas chamber enters the microbubble generator 82 through the return gas pipe 84, and is then injected into the cyclone chamber 22 as tiny bubbles. This creates a circulation system, eliminating the need for additional gas or water supply and achieving a sealed, oxygen-free environment.

[0048] It is easy to understand that the “mud,” “solid phase,” and “solid phase particles” in this invention refer to the same substance, namely, solid impurities in the fracturing flowback fluid.

[0049] The oil-water interface meter and microbubble generator 82 involved in this invention are both existing devices that can achieve the corresponding functions. Their specific internal structures are not the design focus of this invention and will not be described in detail here.

[0050] The invention will now be described through a specific embodiment. In this specific embodiment, the high-efficiency treatment and sludge thickening device 100 for fracturing flowback fluid includes an electrocoagulator 1 formed by five flocculation tubes 11 connected in series and a settling tank 2. The flocculation tubes 11 are DN50×1000mm in size, the settling tank 2 is DN500×2000mm in size, the entire skid-mounted device occupies an area of ​​2000mm×1000mm×2000mm, and the processing capacity is 5m³. 3 / h. The five-stage flocculation tube 11 is arranged longitudinally, with aluminum anodes used in the rod-shaped anodes 112. The power supply 13 controls the voltage to 5-9V and the current to 50-100A. Difficult-to-separate oilfield wastewater, such as fracturing flowback fluid, undergoes electrocoagulation treatment, removing most of the oil droplets, suspended impurities, and solid impurities without or with minimal chemical addition. The treated water then swirls into the settling tank 2. The return flow rate of the microbubble generator 82 in the settling tank 2 is 1.0 m³ / h. 3 / h, return gas volume 0.7m³ 3 / h. The bubbles generated and released by the microbubble generator 82 have a particle size of 50-90μm. After entering the settling cylinder 2 through the dissolved air water release pipe 83, they are mixed and adhered to the fracturing flowback fluid through the conical cyclone separator 25. The cyclone separation accelerates the separation of flocs, oil droplets and water. Most of the sludge formed settles into the sludge collection bin 23 for storage.

[0051] As the fracturing flowback fluid continues to flow, the inclined conical baffles 5 and baffle tubes 7 further enhance the coalescence of oil droplets, accelerating their upward movement, while simultaneously speeding up the settling of sludge and other impurity particles. The sludge formed from solid particles enters the sludge collection chamber 23 for storage through the sludge sliding pipe 6 at the bottom of the conical baffles 5. The purified water and accumulated oil layer are discharged from the drain outlet 92 and oil outlet 91 at the top of the settling tank 2, respectively. The effluent has an oil content ≤50 mg / L and a suspended solids content ≤50 mg / L, meeting the filter influent requirements. When used with filters of different gradations, it can effectively adapt to the water injection requirements of different oil reservoirs. The sludge treated using this invention has a water content below 85%, significantly reducing the volume of high-water-content sludge and lowering subsequent transportation and treatment costs.

[0052] This invention first demulsifies and flocculates the fracturing flowback fluid. Demulsification lays the foundation for the separation of emulsified oil and water, while flocculation initially separates oil droplets, suspended impurities, and solid phases from the water. Subsequently, the settling tank 2 separates the oil, water, and mud from the fracturing flowback fluid. This invention is suitable for short-process, high-efficiency treatment of difficult-to-separate oilfield wastewater such as fracturing flowback fluid, wellhead spray fluid, well washing, and operational wastewater. It can also be used for wastewater treatment in ordinary oil and gas fields with high solid impurities, limited space, and high water quality requirements. It is particularly suitable for demulsification, oil removal, and purification of operational wastewater such as fracturing flowback fluid with high emulsification and many impurities. Through a reasonable internal structural design, this invention can achieve closed-loop, oxygen-free, continuous treatment, resulting in high efficiency, low (or no) chemical dosage, low operating costs, small device size, and easy skid-mounting.

[0053] In the description of this invention, it should be understood that the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this invention, "a plurality of" means two or more, unless otherwise explicitly specified.

[0054] In this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0055] In the description of this specification, references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0056] Finally, it should be noted that the above description is merely a preferred embodiment of the present invention and does not constitute any limitation on the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A high-efficiency treatment and sludge thickening device for fracturing flowback fluid, characterized in that, include: An electrocoagulant (1) includes multiple flocculation tubes (11) arranged in parallel and connected in series, a U-shaped connector (12) connected between adjacent flocculation tubes, and a power supply (13) for supplying power to the flocculation tubes. The adjacent flocculation tubes are connected by the U-shaped connector to form a bent pipeline. The turbulent effect of the bend is conducive to the formation, aggregation and growth of flocs. Settling cylinder (2) is used to separate oil, water and mud from fracturing flowback fluid. The separated mud is deposited and concentrated at the bottom of the settling cylinder. A first conical mud hopper (21) and a conical vortex separator (25) are provided inside the settling cylinder (2). The first conical slurry bucket (21) divides the settling cylinder into a vortex chamber (22) and a mud collection chamber (23). A mud collection port (211) connecting the vortex chamber and the mud collection chamber is provided at the lower end of the first conical slurry bucket. A conical baffle (5) is provided on the central axis of the settling cylinder (2). The conical baffle is located above the first conical sludge hopper (21). The conical baffle is configured as an inverted cone. The upper diameter of the conical baffle is larger than the diameter of the top of the conical cyclone separator but smaller than the inner diameter of the settling cylinder. A sludge-sliding pipe (6) is provided connecting the bottom end of the conical baffle (5) and the sludge collection bin (23). A baffle cylinder (7) is provided above the conical baffle (5). The upper diameter of the baffle cylinder is equal to the diameter of the settling cylinder (2), and the lower diameter of the baffle cylinder is smaller than the upper diameter of the conical baffle (5). A flow-deflecting channel is formed between the baffle cylinder and the conical baffle. An oil collection tank (95) is provided inside the settling cylinder (2). The oil collection tank (95) is used to control the liquid level, thereby forming an air cavity at the top of the settling cylinder (2) for connecting the return gas pipe (84). The high-efficiency treatment and sludge thickening device for fracturing flowback fluid also includes a return water pipe (85) extending from the settling cylinder (2). The first conical sludge hopper is located below the return water pipe (85). The cyclone tube (3) is connected to the outlet end of the electrocoagulant and extends into the settling cylinder along the tangential direction of the cross-section of the settling cylinder. The return water pipe (85) is located below the cyclone tube (3).

2. The high-efficiency treatment and sludge thickening device for fracturing flowback fluid according to claim 1, characterized in that, An insulating flange (14) is provided between the flocculation pipe (11) and the U-shaped joint (12). The flocculation pipe (11) includes a hollow pipe (111) connected to the cathode of the power source (13) and a rod-shaped anode (112) connected to the anode of the power source. The hollow pipe (111) is an electrical conductor, and the rod-shaped anode is intermittently sleeved inside the hollow pipe.

3. The high-efficiency treatment and sludge thickening device for fracturing flowback fluid according to claim 2, characterized in that, The high-efficiency treatment and sludge thickening device for fracturing flowback fluid also includes a dissolved air water release pipe (83) extending into the settling cylinder (2), and a microbubble generator (82) connecting the return water pipe (85) and the dissolved air water release pipe (83). The dissolved air water release pipe is arranged along the tangent of the cross section of the settling cylinder (2) and is used to transport the dissolved air water generated by the microbubble generator (82) into the settling cylinder (2).

4. The high-efficiency treatment and sludge thickening device for fracturing flowback fluid according to claim 3, characterized in that, The dissolved air water release pipe (83) is above the vortex tube (3), the microbubble generator (82) is connected to the top of the settling cylinder (2) through the return air pipe (84), and the return water pipe (85) is connected to the microbubble generator (82) through the return water pump (81).

5. The high-efficiency treatment and sludge thickening device for fracturing flowback fluid according to claim 4, characterized in that, A sludge discharge port (231) is provided at the bottom of the sludge collection bin.

6. The high-efficiency treatment and sludge thickening device for fracturing flowback fluid according to claim 5, characterized in that, Inside the settling cylinder (2), a vortex generator (24) is also provided. The vortex generator is located below the swirling pipe (3) and directly above the mud collection port (211), and can block the swirling intensity in the swirling chamber (22) from being transmitted to the mud collection chamber (23).

7. The high-efficiency treatment and sludge thickening device for fracturing flowback fluid according to claim 6, characterized in that, The inner diameter of the upper end of the conical cyclone separator is smaller than the inner diameter of the lower end.

8. The high-efficiency treatment and sludge thickening device for fracturing flowback fluid according to claim 7, characterized in that, A second conical sludge bucket (26) is provided at the top of the conical cyclone separator (25). The upper diameter of the second conical sludge bucket is equal to the diameter of the settling cylinder (2), and the lower diameter of the second conical sludge bucket is equal to the top diameter of the conical cyclone separator (25).

9. The high-efficiency treatment and sludge thickening device for fracturing flowback fluid according to claim 8, characterized in that, The conical baffle is located above the second conical mud hopper (26).

10. The high-efficiency treatment and sludge thickening device for fracturing flowback fluid according to claim 1, characterized in that, An oil drain port (91) and a drain port (92) are provided on the outer shell of the settling cylinder (2) above the baffle cylinder (7). The oil drain port (91) is located above the drain port (92), and the oil drain port (91) and the drain port (92) are respectively located at the radial ends of the settling cylinder (2).

11. The high-efficiency treatment and sludge thickening device for fracturing flowback fluid according to claim 10, characterized in that, The oil collection trough (95) is fastened to the oil outlet, and an opening is provided at the top of the oil collection trough (95).

12. The high-efficiency treatment and sludge thickening device for fracturing flowback fluid according to claim 11, characterized in that, A conical wide-mouth oil-water separator (93) is provided above the baffle (7). The oil outlet (91) is located above the conical wide-mouth oil-water separator (93), and the drain outlet (92) is located on the settling cylinder (2) at the lower part corresponding to the conical wide-mouth oil-water separator (93).

Images