Oil removal system and process for oilfield produced water

Abstract

The invention provides an oil removal system and process for oilfield produced water, the oil removal system comprises a control system, a buffer glue breaking water tank, a pressure pump and a coalescence cyclone separator, the buffer glue breaking water tank is communicated with the pressure pump through a water outlet pipeline, and the other end of the pressure pump is communicated with the coalescence cyclone separator; a flow meter and an inlet electric valve are sequentially mounted on the water inlet pipeline in the water flow direction; the water inlet pipeline is communicated with a bypass pipeline, the other end of the bypass pipeline is communicated with the coalescence cyclone separator through a communication pipeline, and a first pressure transmitter is installed on the bypass pipeline. The buffer glue breaking water tank is arranged for carrying out glue breaking pretreatment, the treated water is subjected to coalescence and then swirling through the coalescence cyclone separator, oil drops rapidly collide and coalesce with one another and are separated in the water, and the oil drops in the produced water are rapidly and efficiently removed. Meanwhile, a flowmeter, a pressure transmitter, an electric valve and a liquid level detection and linkage system are arranged at an inlet and an outlet, so that automatic detection, automatic adjustment and automatic operation of the oil removal system are realized.

Description

Technical Field

[0001] The present invention belongs to the technical field of oilfield produced water treatment, and particularly relates to an oil removal system and process for oilfield produced water. Background Art

[0002] Oilfield produced water generally has the characteristics of high oil content, high suspended solid particle content, high salinity, and strong corrosiveness. During the oilfield production process, most of the oilfield produced water is treated and then reinjected into the formation. Therefore, there are strict requirements for the oil content and suspended solid particle content in the water of oilfield produced water. Oilfield produced water generally uses a settling oil removal tank for preliminary oil-water separation. The oil-water mixture flows into the water layer at the bottom of the settling tank through the inlet pipeline, the liquid distribution center header pipe, and the radial liquid distribution pipe. Through gravity settling separation, the oil in the water floats and the suspended solids in the water sink. The floating oil after settling separation enters the oil collection tank and flows out of the settling tank through the overflow pipe; the produced water after settling separation is discharged through the middle and lower water distribution pipes. The settling oil removal tank operates with two tanks. Using the principle of gravity settling, the separation efficiency is low, the floor area is large, the investment is high, and the construction period is long.

[0003] An oil removal device for oilfield produced water (CN202020330756.3) publicly disclosed by the State Intellectual Property Office on October 27, 2020, includes a tank body. A bearing is fixedly connected to the top of the tank body. The bearing penetrates through the top of the tank body. The inner ring of the bearing is fixedly connected to a rod body. One end of the rod body away from the tank body is fixedly connected to the output shaft of a motor. The outer side wall of the rod body is respectively fixedly connected with a box body and a pipe body. The outer side wall of the pipe body is fixedly connected with a plate body. The inner side wall of the tank body is fixedly connected with a shell; through structures such as a motor, a rod body, and a plate body, the present invention creates a vortex in the tank body to accelerate the separation of oil and water, can quickly pump out the upper oil layer, quickly drain water and discharge sludge, with short time consumption and good effect, thereby improving work efficiency, saving time, and saving costs. However, the separation effect on severely emulsified produced water is poor, which limits the oil-water separation effect. Summary of the Invention

[0004] The purpose of the present invention is to provide an oil removal system for oilfield produced water, which can efficiently remove oil.

[0005] Another purpose of the present invention is to provide an oil removal process for oilfield produced water, with an oil and suspended solid removal rate of 90-95% for oilfield produced water, and the removal particle size ≥ 10 μm.

[0006] Therefore, the technical solutions provided by the present invention are as follows: An oil removal system for produced water in oil fields, comprising a control system, a buffer and demulsification water tank, a pressure pump, and a coalescing hydrocyclone separator. The buffer and demulsification water tank is connected to a water inlet pipeline. The buffer and demulsification water tank is connected to the pressure pump through a water outlet pipeline. The other end of the pressure pump is connected to the coalescing hydrocyclone separator. A flow meter and an inlet electric valve are sequentially installed on the water inlet pipeline along the water flow direction; The water inlet pipeline is connected to a bypass pipeline, and the connection point is located between the flow meter and the inlet electric valve. The other end of the bypass pipeline is connected to the coalescing hydrocyclone separator through a connection pipeline. A bypass electric valve is installed on the bypass pipeline. A pressure transmitter I is installed on the bypass pipeline. The pressure transmitter I, the pressure pump, the flow meter, the inlet electric valve, and the bypass electric valve are all electrically connected to the control system. The buffer and demulsification water tank includes a tank body and an air-blowing device. A demulsification packing structure is arranged in the middle of the tank body. The spaces between the two sides of the demulsification packing structure and the tank body are respectively an inlet sedimentation area and a water collection sedimentation area. An oil collection pipeline is connected to the top of the tank body. Both ends of the air-blowing device pass through the demulsification packing structure; The inlet sedimentation area is connected to the lower part of the demulsification packing structure. The water collection sedimentation area is connected to the upper part of the demulsification packing structure. The inlet sedimentation area is connected to the water inlet pipeline. The water outlet pipeline is connected to the water collection sedimentation area. The lower parts of the inlet sedimentation area and the water collection sedimentation area are both funnel-shaped and connected to a sludge discharge pipeline.

[0007] The demulsification packing structure includes multiple sections of packing areas. The upper part of the first section of packing area is isolated from the inlet sedimentation area, and the lower part of the first section of packing area is communicated with the inlet sedimentation area. The upper part of the second section of packing area is connected to the upper part of the first section of packing area and isolated from the upper part of the third section of packing area. The lower part of the second section of packing area is connected to the lower part of the third section of packing area. This is cyclically arranged. The upper part of the last section of packing area is connected to the water collection sedimentation area.

[0008] The inlet end of the coalescing hydrocyclone separator is connected with a coalescing pipe through a flange, and the coalescing pipe is filled with coalescing packing.

[0009] A pressure transmitter II is installed on the connection pipeline between the bypass pipeline and the coalescing hydrocyclone separator. The water outlet and oil outlet of the coalescing hydrocyclone separator are respectively arranged at both ends of the body.

[0010] It also includes a standby pressure pump. A liquid level gauge is installed on the top of the buffer and demulsification water tank, and the liquid level gauge is linked with the pressure pump and the standby pressure pump.

[0011] An oil removal process for produced water in oilfields uses an oil removal system for produced water in oilfields. The water coming from the three-phase separator is metered by a flowmeter and then enters the buffer and demulsification water tank for demulsification reaction. When the set liquid level is reached, it is pressurized by a pressure pump and enters the coalescing hydrocyclone separator for oil-water separation. The treated produced water after separation enters the subsequent treatment through the outlet valve, the separated oil is connected to the waste oil storage through the oil drain valve, and the separated sludge is connected to the sludge pool through the sludge drain valve.

[0012] When the produced water is non-emulsified produced water, the water coming from the three-phase separator is metered by a flowmeter and then undergoes pressure detection through a pressure transmitter I. When the incoming water pressure is lower than the set pressure, the inlet electric valve opens and the bypass electric valve closes, and the incoming water enters the buffer and demulsification water tank. After being pressurized by a pressure pump, it enters the coalescing hydrocyclone separator for separation. When the incoming water pressure reaches the set pressure, the inlet electric valve closes and the bypass electric valve opens, and the incoming water enters the coalescing hydrocyclone separator for separation.

[0013] After the water from the three-phase separator enters the buffer and demulsification water tank through the water inlet pipeline, it is mixed with the produced water through the air injection device to form a steam-water mixture. The mixture undergoes demulsification reaction through the demulsification filler. After reacting successively through multiple filler areas of the demulsification filler structure, it enters the water collection and sedimentation area and finally flows out through the water outlet pipeline. The sludge formed during the entire reaction process is discharged from the box body through the bottom sludge discharge pipeline.

[0014] The beneficial effects of the present invention are: The oil removal system for produced water in oilfields provided by the present invention performs demulsification pretreatment by setting a buffer and demulsification water tank. The treated water is first coalesced and then swirled through the coalescing hydrocyclone separator, and the oil droplets quickly collide with each other, coalesce, and separate in the water, realizing the rapid and efficient removal of oil droplets (or suspended matter) in the produced water. At the same time, flowmeters, pressure transmitters, electric valves, liquid level detection and linkage systems are set at the inlet and outlet to realize the automatic detection, automatic adjustment, and automatic operation of the oil removal system.

[0015] The process of the present invention adopts different oil removal processes according to the different incoming water pressures. When the pressure is lower than the set pressure, it is demulsified by the buffer and demulsification water tank, pressurized by a pressure pump, and then enters the coalescing hydrocyclone separator for separation treatment; when the pressure is greater than the set pressure, the incoming water directly enters the coalescing hydrocyclone separator for separation treatment. The present invention automatically adjusts the process, has high separation efficiency and good separation effect. Description of the Drawings

[0016] Figure 1 is a schematic structural diagram of an embodiment of the system of the present invention; Figure 2 is a schematic structural diagram of an embodiment of the buffer and demulsification water tank; Figure 3 is a process flow diagram of the method of the present invention.

[0017] In the figure: 1. Buffer gel-breaking water tank; 2. Pressurized pump; 3. Standby pressurized pump; 4. Coalescing hydrocyclone separator; 5. Flowmeter; 6. Pressure transmitter I; 7. Inlet electric valve; 8. Bypass electric valve; 9. Pressure transmitter II; 10. Outlet valve; 11. Oil discharge valve; 12. Sludge discharge valve; 13. Water inlet pipeline; 14. Water outlet pipeline; 15. Oil collection pipeline; 16. Sludge discharge pipeline; 17. Air-blowing device; 18. Gel-breaking filler structure; 19. Bypass pipeline; 20. Liquid level gauge; 21. Coalescing pipe. Detailed implementation mode

[0018] The following specific embodiments illustrate the implementation mode of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification.

[0019] Now, refer to the accompanying drawings to introduce the exemplary implementation mode of the present invention. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. These embodiments are provided to disclose the present invention in detail and completely, and to fully convey the scope of the present invention to those skilled in the art. The terms in the exemplary implementation modes shown in the accompanying drawings are not limitations on the present invention. In the drawings, the same units / components use the same reference numerals.

[0020] Unless otherwise specified, the terms (including scientific and technical terms) used herein have the ordinary meaning understood by those skilled in the art. In addition, it can be understood that the terms defined in the commonly used dictionary should be understood to have a meaning consistent with the context of their related fields, and should not be understood as idealized or overly formal meanings.

[0021] Embodiment 1 This embodiment provides an oil removal system for produced water in oil fields, as Figure 1 shown, including a control system, a buffer gel-breaking water tank 1, a pressurized pump 2, and a coalescing hydrocyclone separator 4. The buffer gel-breaking water tank 1 is connected to a water inlet pipeline 13. The buffer gel-breaking water tank 1 is connected to the pressurized pump 2 through a water outlet pipeline 14. The other end of the pressurized pump 2 is connected to the coalescing hydrocyclone separator 4. A flowmeter 5 and an inlet electric valve 7 are sequentially installed on the water inlet pipeline 13 along the water flow direction; The water inlet pipeline 13 is connected to a bypass pipeline 19, and the connection point is located between the flowmeter 5 and the inlet electric valve 7. The other end of the bypass pipeline 19 is connected to the coalescing hydrocyclone separator 4 through a connecting pipeline. A bypass electric valve 8 is installed on the bypass pipeline 19. A pressure transmitter I 6 is installed on the bypass pipeline 19. The pressure transmitter I 6, the pressurized pump 2, the flowmeter 5, the inlet electric valve 7, and the bypass electric valve 8 are all electrically connected to the control system. Working principle: After the water from the three-phase separator is metered by the flowmeter 5, it enters the buffer demulsification water tank 1 or directly enters the coalescing hydrocyclone separator 4 according to the pressure detected by the pressure transmitter 6 and the set pressure. After undergoing demulsification treatment in the buffer demulsification water tank 1, the sewage and overflow water are both connected to the sewage tank, the separated oil enters the oil tank, the treated water is pressurized by the booster pump 2 and enters the coalescing hydrocyclone separator 4 for oil-water separation, the treated water is connected to the buffer tank, the waste oil is connected to the waste oil recovery device, and the sludge is discharged from the bottom into the sludge tank.

[0022] This oilfield produced water deoiling system provided by the present invention performs demulsification pretreatment by setting up the buffer demulsification water tank 1. The treated water passes through the coalescing hydrocyclone separator 4 in a way of first coalescing and then swirling. The oil droplets quickly collide with each other, coalesce, and separate in the water, realizing the rapid and efficient removal of oil droplets (or suspended solids) in the produced water. At the same time, flowmeters 5, pressure transmitters, electric valves, and liquid level detection and linkage systems are set at the inlet and outlet to achieve automatic detection, automatic adjustment, and automatic operation of this deoiling system.

[0023] Example 2 Based on Example 1, this example provides an oilfield produced water deoiling system, as Figure 2 shown. The buffer demulsification water tank 1 includes a box body and an air-blowing device 17. A demulsification filler structure 18 is provided in the middle of the box body. The spaces between the two sides of the demulsification filler structure 18 and the box body are respectively an inlet sedimentation area and a water collection sedimentation area. An oil collection pipeline 15 is connected to the top of the box body, and both ends of the air-blowing device 17 pass through the demulsification filler structure 18; The inlet sedimentation area is connected to the lower part of the demulsification filler structure 18, the water collection sedimentation area is connected to the upper part of the demulsification filler structure 18, the inlet sedimentation area is connected to the inlet pipeline 13, the outlet pipeline 14 is connected to the water collection sedimentation area, and the lower parts of both the inlet sedimentation area and the water collection sedimentation area are funnel-shaped and connected to a sludge discharge pipeline 16.

[0024] The water from the three-phase separator enters the buffer demulsification water tank 1 through the inlet pipeline 13, is mixed with the produced water by the air-blowing device 17 to form a steam-water mixture, the mixture undergoes a demulsification reaction through the demulsification filler structure 18 and then enters the water collection sedimentation area, and finally flows out through the outlet pipeline 14. The whole reaction process forms sludge, which is discharged from the box body through the bottom sludge discharge pipeline 16.

[0025] Example 3 On the basis of Embodiment 2, this embodiment provides an oil removal system for produced water in oilfields. The gel-breaking packing structure 18 includes multiple packing zones. The upper part of the first packing zone is isolated from the inlet settling zone, and the lower part of the first packing zone communicates with the inlet settling zone. The upper part of the second packing zone communicates with the upper part of the first packing zone and is isolated from the upper part of the third packing zone. The lower part of the second packing zone communicates with the lower part of the third packing zone, and so on in a cyclic arrangement. The upper part of the last packing zone communicates with the water collection and settling zone.

[0026] As Figure 2 shown, the gel-breaking packing structure 18 includes three packing zones. The water from the three-phase separator enters the inlet settling zone through the inlet pipeline 13, then enters the lower part of the first packing zone, passes through the packing layer and enters the packing layer of the second packing zone from the upper part, then enters the lower part of the third packing zone from the lower part of the second packing zone, and finally is discharged into the water collection and settling zone through the upper part of the third packing zone. The oil-free water finally passes through the outlet pipeline 14 and is discharged into the booster pump 2.

[0027] Embodiment 4 On the basis of Embodiment 1, this embodiment provides an oil removal system for produced water in oilfields. The inlet end of the coalescing hydrocyclone 4 is connected with a coalescing pipe 21 through a flange, and the coalescing pipe 21 is filled with coalescing packing.

[0028] As Figure 1 shown, the top inlet of the coalescing hydrocyclone 4 is connected with a coalescing pipe 21 through a flange. The stainless steel coalescing packing in the coalescing pipe 21 coalesces the oil in the water and then enters the hydrocyclone for oil removal. In this embodiment, the specification of the coalescing pipe 21 is DN200, and the length is 300 - 500 mm.

[0029] Embodiment 5 On the basis of Embodiment 1, this embodiment provides an oil removal system for produced water in oilfields. A pressure transmitter II 9 is installed on the connecting pipeline between the bypass pipeline 19 and the coalescing hydrocyclone 4. The water outlet and oil outlet of the coalescing hydrocyclone 4 are respectively arranged at both ends of the body.

[0030] It further includes a standby booster pump 3. A liquid level gauge 20 is installed on the top of the buffer gel-breaking water tank 1, and the liquid level gauge 20 is linked with the booster pump 2 and the standby booster pump 3.

[0031] The pressure transmitter II 9 is used for on-line detection of the inlet pressure of the coalescing hydrocyclone 4. When the level of the treated water in the buffer gel-breaking water tank 1 reaches the upper limit of the liquid level as detected by the liquid level gauge 20, the booster pump 2 is started to pressurize the liquid and then discharge it into the coalescing hydrocyclone 4 for oil-water separation.

[0032] Embodiment 6 This embodiment provides an oil removal process for produced water in oilfields. AsFigure 3 As shown, the water from the three-phase separator enters the buffer and demulsification water tank 1 for demulsification reaction after being measured by the flowmeter 5. When the set liquid level is reached, it is pressurized by the pressure pump 2 and enters the coalescing hydrocyclone separator 4 for oil-water separation. The produced water after separation enters the subsequent treatment through the outlet valve 10, the separated oil is connected to the waste oil storage through the oil discharge valve 11, and the separated sludge is connected to the sludge pool through the sludge discharge valve 12.

[0033] The present invention can achieve efficient demulsification and separation of oil and suspended solids contained in the produced water of oil fields. The removal rates of oil and suspended solids in the produced water of oil fields reach 90 - 95%, the removal particle size is ≥ 10 μm, and the residence time is 5 - 8S.

[0034] Example 7 Based on Example 6, this example provides an oil removal process for the produced water of oil fields. When the produced water is non-emulsified produced water, the water from the three-phase separator enters the buffer and demulsification water tank 1 after being measured by the flowmeter 5 and undergoes pressure detection by the pressure transmitter 6. When the incoming water pressure is lower than the set pressure, the inlet electric valve 7 opens and the bypass electric valve 8 closes, and the incoming water enters the buffer and demulsification water tank 1, and after being pressurized by the pressure pump 2, it enters the coalescing hydrocyclone separator 4 for separation; When the incoming water pressure reaches the set pressure, the inlet electric valve 7 closes and the bypass electric valve 8 opens, and the incoming water enters the coalescing hydrocyclone separator 4 for separation.

[0035] After the water from the three-phase separator enters the buffer and demulsification water tank 1 through the water inlet pipeline 13, it is mixed with the produced water through the air injection device 17 to form a steam-water mixture. The mixture undergoes demulsification reaction through the demulsification filler, and after reacting in multiple filler zones of the demulsification filler structure 18, it enters the water collection and sedimentation area, and finally flows out through the water outlet pipeline 14. The sludge formed during the entire reaction process is discharged from the box through the bottom sludge discharge pipeline 16.

[0036] In Figure 1 , the present invention is implemented through two operation modes. The first mode is for non-emulsified produced water. The water from the three-phase separator enters the buffer and demulsification water tank 1 after being measured by the flowmeter 5 and undergoes pressure detection by the pressure transmitter 6. When the incoming water pressure is lower than 0.35 MPa, the inlet electric valve 7 opens and the bypass electric valve 8 closes, and the incoming water enters the buffer and demulsification water tank 1, and after being pressurized by the pressure pump 2 or the standby pressure pump 3, it enters the coalescing hydrocyclone separator 4 for separation. When the incoming water pressure reaches 0.35 MPa, the inlet electric valve 7 closes and the bypass electric valve 8 opens, and the incoming water enters the coalescing hydrocyclone separator 4 for separation. The pressure transmitter 9 conducts on-line detection of the inlet pressure of the coalescing hydrocyclone separator 4. The produced water after separation enters the subsequent treatment through the outlet valve 10, the separated oil is connected to the waste oil storage through the oil discharge valve 11, and the separated sludge is connected to the sludge pool through the sludge discharge valve 12.

[0037] Method 2: For emulsified produced water, after the water from the three-phase separator is metered by the flowmeter 5, the inlet electric valve 7 is opened and the bypass electric valve 8 is closed, and the water enters the buffer and demulsification water tank 1. After being pressurized by the pressurizing pump 2 or the standby pressurizing pump 3, it enters the coalescing hydrocyclone separator 4 for separation.

[0038] When the device needs to be overhauled and maintained, the inlet electric valve 7 is closed and the bypass electric valve 8 is opened, and the water enters the coalescing hydrocyclone separator 4 for separation. The pressure transmitter II 9 performs on-line detection of the inlet pressure of the coalescing hydrocyclone separator 4. The separated produced water enters the subsequent treatment through the outlet valve 10, the separated oil is connected to the waste oil storage through the oil drain valve 11, and the separated sludge is connected to the sludge pool.

[0039] The above examples are only illustrative of the present invention and do not constitute a limitation on the protection scope of the present invention. Any design identical or similar to the present invention falls within the protection scope of the present invention.

Claims

1. An oilfield produced water deoiling system, characterized in that: It includes a control system, a buffering and breaking glue water tank, a pressure pump and a coalescing and cyclone separator. The buffering and breaking glue water tank is connected to a water inlet pipeline, and the buffering and breaking glue water tank is connected to a pressure pump through a water outlet pipeline. The other end of the pressure pump is connected to the coalescing and cyclone separator. A flow meter and an inlet electric valve are sequentially installed on the water inlet pipeline along the water flow direction; The water inlet pipeline is connected to a bypass pipeline, and the connection point is arranged between the flow meter and the inlet electric valve. The other end of the bypass pipeline is connected to the coalescing cyclone separator through the connecting pipeline. The bypass pipeline is installed with a bypass electric valve. The bypass pipeline is installed with a pressure transmitter 1. The booster pump, the pressure transmitter 1, the flow meter, the inlet electric valve and the bypass electric valve are all connected with the control system electrical signal.

2. The oil field produced water deoiling system according to claim 1, characterized in that: The water inlet sedimentation area is connected with the lower part of the gel-breaking filler structure, the water collection sedimentation area is connected with the upper part of the gel-breaking filler structure, the water inlet sedimentation area is connected with the water inlet pipeline, the water outlet pipeline is connected with the water collection sedimentation area, and the lower parts of the water inlet sedimentation area and the water collection sedimentation area are both funnel-shaped and connected with a mud discharge pipeline.

3. The oil field produced water deoiling system according to claim 1, characterized in that: The inlet end of the coalescing cyclone separator is connected to a coalescing tube via a flange, and the coalescing tube is filled with coalescing fillers.

4. The oil field produced water deoiling system according to claim 1, characterized in that: A second pressure transmitter is installed on the bypass pipeline and the connecting pipeline of the coalescing cyclone separator. The water outlet and the oil outlet of the coalescing cyclone separator are respectively arranged at two ends of the body.

5. The oil field produced water deoiling system according to claim 1, characterized in that: It also includes a spare pressure pump. A liquid level gauge is installed on the top of the buffer glue breaking water tank. The liquid level gauge is linked with the pressure pump and the spare pressure pump.

6. An oilfield produced water deoiling process, using the oilfield produced water deoiling system according to claim 2, characterized in that: The water from the three-phase separator is measured by the flow meter and then enters the buffer water tank for gel breaking reaction. When the set liquid level is reached, it is pressurized by the pressure pump and enters the coalescing cyclone separator for oil-water separation. After separation, the produced water enters the subsequent treatment through the outlet valve. After separation, the oil is connected to the waste oil storage through the oil discharge valve, and the sludge is connected to the sludge pool through the sludge discharge valve.

7. The oil field produced water deoiling process according to claim 6, characterized in that: When the produced water is non-emulsified produced water, the water from the three-phase separator is measured by the flow meter and then pressure detected by the pressure transmitter. When the incoming water pressure is lower than the set pressure, the inlet electric valve opens, the bypass electric valve closes, and the incoming water enters the buffer degelatinizing water tank, and after being pressurized by the booster pump, it enters the coalescing cyclone separator for separation; when the incoming water pressure reaches the set pressure, the inlet electric valve closes, the bypass electric valve opens, and the incoming water enters the coalescing cyclone separator for separation.

8. The oil field produced water deoiling process according to claim 6, characterized in that: After the water from the three-phase separator enters the buffer degelling water tank through the water inlet pipeline, it is mixed with the produced water through the aeration device to form a steam-water mixture. The mixture undergoes a degelling reaction through the degelling filler, and after reacting in multiple filler areas of the degelling filler structure, it enters the water collection and sedimentation area and finally flows out through the water outlet pipeline. The sludge formed during the entire reaction process is discharged from the box through the bottom sludge discharge pipeline.

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