Oilfield produced water filtering device and method

Abstract

The invention provides an oilfield produced water filtering device and method, the device comprises a reinforced oil removal unit, a primary filtering unit and a secondary filtering unit, a water outlet of the reinforced oil removal unit is communicated with the primary filtering unit, and the primary filtering unit is communicated with the secondary filtering unit through a water outlet pipeline. The enhanced oil removal unit is arranged in front of the primary filter unit, so that oil in produced water is effectively removed. Produced water tangentially enters a conical oil removal funnel of the reinforced oil removal unit through a water inlet pipeline, water is guided into the conical oil removal funnel to form a rotational flow state through a rotational flow channel arranged inside, and oil enters the top of the conical oil removal funnel due to different gravity of oil and water in the rotational flow flowing process; and the separated oil is recovered through the oil recovery pipeline and removed from the water treatment system, so that oil removal is realized, the frequency of polluting the filter by the dirty oil and the backwashing frequency are reduced, the effluent quality of the filter is improved, and meanwhile, the dirty oil in produced water is further recycled.

Description

Technical Field

[0001] The present invention belongs to the technical field of oilfield produced water treatment, and particularly relates to an oilfield produced water filtration device and method. Background Art

[0002] With the continuous exploitation of oilfields, the water cut of oilfield produced fluids has been increasing year by year. Oilfield produced water is the oily sewage separated from crude oil dehydration during oil production operations, which contains oils (about 1000 - 2000 mg / L, sometimes even up to 5000 mg / L, mainly in the forms of floating oil, dispersed oil, emulsified oil and dissolved oil), suspended solids (generally 100 - 1000 mg / L, mainly including FeS particles, silt and fine sand, etc.), salt content (concentration range 10 3 -10 6 mg / L, mainly including Ca 2+ 、Mg 2+ 、K + 、Na + 、Fe 2+ 、Cl - 、HCO 3 - 、CO 3 2- etc.), organic matters (including aliphatic hydrocarbons, aromatic hydrocarbons, phenols, organic sulfides, fatty acids, surfactants, polymers, etc.) and microorganisms (mainly sulfate-reducing bacteria, saprophytic bacteria and iron bacteria, etc.). Comprehensively treating the oilfield produced water generated during the crude oil exploitation process and reinjecting it locally can save water quality resources for injection, reduce environmental pollution caused by sewage, and effectively supplement formation energy. At present, fine filtration devices are generally used as the main treatment unit for water quality control in oilfield produced water treatment, and the backend fine filtration adopts primary filtration, secondary filtration or tertiary filtration to meet the reinjection index.

[0003] For the invention patent with the patent number 201910459110.7 and the patent name "An integrated oilfield produced water filtration and separation device" announced on July 30, 2019, the separation device includes a tank body, and the tank body includes an oil removal chamber, a multi-stage filtration chamber and a buffer chamber that are sequentially connected in the axial direction. Among them, a liquid inlet is arranged on the side wall of the oil removal chamber, an oil removal inclined plate is arranged inside the oil removal chamber, and an exhaust port is opened on the upper wall of the oil removal chamber; the multi-stage filtration chamber includes a plurality of filtration chambers, a filtration medium is arranged inside each filtration chamber, and a backwash pipe extending into the filtration medium is arranged in each filtration chamber; a buffer baffle is arranged inside the buffer chamber, and a liquid outlet is opened on the lower wall of the buffer chamber. This filtration and separation device adopts an integrated multi-stage multi-medium filtration, with a high degree of integration, convenient management, shortening the oil removal and impurity removal treatment time of oilfield reinjected water, and improving the overall working efficiency. The above-mentioned oil filtration and separation device is not thorough in oil removal. The produced water enters the fine filtration treatment process from the back end of the oil removal unit. Since the fine filtration device is mainly aimed at removing suspended solids, the effect on oil removal is not very good. The produced water with high oil content and high emulsification is likely to cause serious pollution to the filter when it enters the filter. After the filter is polluted, there are a series of problems such as difficult backwashing, incomplete backwashing, filter media caking, and decreased filtration capacity, resulting in a decrease in the subsequent treatment capacity of the filter, a deterioration in the overall quality of the treated effluent, and failure to meet the injection water quality standards. Summary of the Invention

[0004] The purpose of the present invention is to provide an oilfield produced water filtration device to overcome the above-mentioned technical problems existing in the prior art.

[0005] Another purpose of the present invention is to provide an oilfield produced water filtration method, which can reduce the filtration treatment load, reduce the frequency of pollution of the filtration device by dirty oil and the number of backwashing times, improve the effluent quality of the filtration device, and at the same time realize the further recycling of dirty oil in the produced water.

[0006] To this end, the technical solution provided by the present invention is as follows: An oilfield produced water filtration device includes a strengthened oil removal unit, a primary filtration unit, and a secondary filtration unit. The water outlet of the strengthened oil removal unit is connected to the primary filtration unit, and the primary filtration unit is connected to the secondary filtration unit through a water outlet pipeline. The strengthened oil removal unit includes a conical oil removal funnel and a swirl flow channel. The swirl flow channel is arranged on the inner wall of the conical oil removal funnel. The top of the conical oil removal funnel is connected to an oil collection pipeline, and the upper side of the conical oil removal funnel is connected to a water inlet pipeline.

[0007] The middle parts of the primary filtration unit and the secondary filtration unit are both filled with filter media layers. The lower end of the strengthened oil removal unit is arranged in the primary filtration unit and above the filter media layer.

[0008] The bottom end of the conical oil removal funnel is connected to a uniform water distribution device, and the uniform water distribution device adopts a conical screen folding plate.

[0009] The bottom of the primary filtration unit is connected to a first backwash water inlet pipeline, and the upper part of the primary filtration unit is connected to a first backwash sewage discharge pipeline; the bottom of the secondary filtration unit is connected to a second backwash water inlet pipeline, and the upper part of the secondary filtration unit is connected to a second backwash sewage discharge pipeline.

[0010] An oil discharge valve is arranged on the oil collection pipeline, and a viewing window is arranged on the conical oil removal funnel.

[0011] A coalescing oil removal pipe is arranged between the water inlet pipeline and the conical oil removal funnel. The coalescing oil removal pipe is filled with coalescing packing, and a flow channel is arranged in the coalescing packing.

[0012] A method for filtering produced water in oil fields uses an oil field produced water filtering device. After the produced water is deoiled by a settling and oil removal tank, it enters the enhanced oil removal unit through the water inlet pipeline. After enhanced oil removal, it enters the primary filtration unit and undergoes primary filtration through the filter media layer. After primary filtration, the produced water enters the secondary filtration unit for secondary filtration. The water discharged from the secondary filtration enters the purified water tank through the drainage pipeline for storage and reinjection.

[0013] The specific process of enhanced oil removal is as follows: The produced water tangentially enters the conical oil removal funnel through the water inlet pipeline. Under the guidance of the swirl flow channel, a swirl flow state is formed inside the conical oil removal funnel. During the swirl flow process, due to the different gravities of oil and water, under the action of centrifugal force, the oil in the water moves in the center of the swirl, gradually downward. Since the bottom of the conical oil removal funnel becomes narrower, a reverse flow is formed, and the oil in the center of the swirl moves upward. Eventually, it enters the top of the conical oil removal funnel. Finally, the separated oil is recovered through the oil collection pipeline and removed from the water treatment system to achieve enhanced oil removal.

[0014] When it is necessary to clean the primary filtration unit and the secondary filtration unit after running for a period of time, the reverse washing water inlet pipeline 1 and the reverse washing water inlet pipeline 2 are respectively connected to the purified water tank for reverse washing, and the reverse washing water is discharged through the reverse washing sewage pipeline 1 and the reverse washing sewage pipeline 2 respectively.

[0015] The beneficial effects of the present invention are as follows: The oil field produced water filtering device provided by the present invention effectively removes the oil in the produced water by setting an enhanced oil removal unit in front of the primary filtration unit. The produced water tangentially enters the conical oil removal funnel of the enhanced oil removal unit through the water inlet pipeline. Through the internally arranged swirl flow channel, the water is guided into the conical oil removal funnel to form a swirl flow state. During the swirl flow process, due to the different gravities of oil and water, under the action of centrifugal force, the oil in the water moves in the center of the swirl, gradually downward. Since the bottom of the conical oil removal funnel becomes narrower, a reverse flow is formed, and the oil in the center of the swirl moves upward. Eventually, it enters the top of the conical oil removal funnel. Then, the separated oil is recovered through the oil collection pipeline and removed from the water treatment system to achieve re - oil removal; the water separated from the periphery of the swirl moves downward and enters the intermediate filtration layer through the bottom outlet of the conical oil removal funnel. To make the water outlet of the conical oil removal funnel more uniform, a uniform water distribution device is set in the conical oil removal funnel. This device uses a screen folded plate to achieve uniform distribution of the water outlet and passes through the bottom filtration layer evenly and stably. The upgrade and transformation of the filter enable the treatment function of the filter to be upgraded from the original simple filtration and interception function to a composite function with coalescence oil removal, swirl oil removal, pressure oil collection, and filtration. The proprietary coalescence swirl oil removal and pressure oil collection structures achieve the improvement of the oil removal capacity in the front section, weaken the influence of upstream oil content fluctuations on the filter, broaden the conditions of the filter inlet water quality, improve the adaptability of the filter, and extend the service life.

[0016] The method of the present invention first performs enhanced oil removal and then filtration. Generally, the water quality requirements at the filtration inlet are: oil content ≤ 50 mg / L, suspended solid content ≤ 60 mg / L. However, the present invention can further improve the water quality indicators at the filter inlet: oil content ≤ 80 - 100 mg / L, suspended solid content ≤ 80 - 100 mg / L. The requirements for the influent water quality are reduced, and the water quality range that the filter can adapt to in the previous stage is broadened. Compared with conventional filters under the same conditions, the filtration treatment load is reduced, the frequency of the filter being contaminated by dirty oil and the number of backwashing times are decreased, the effluent water quality of the filter is improved, and at the same time, further recovery and utilization of the dirty oil in the produced water are achieved. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 is a process schematic diagram of the present invention; Figure 2 is a structural schematic diagram of the enhanced oil removal unit of the present invention; Figure 3 is a structural schematic diagram of the swirl flow channel.

[0018] In the figure: 1. Primary filtration unit; 2. Secondary filtration unit; 3. Inlet pipeline; 4. Outlet pipeline; 5. First backwash inlet pipeline; 6. First backwash sewage discharge pipeline; 7. Enhanced oil removal unit; 8. Oil collection pipeline; 9. Uniform water distribution device; 10. Drainage pipeline; 11. Second backwash inlet pipeline; 12. Second backwash sewage discharge pipeline; 13. Coalescing oil removal pipe; 14. Swirl flow channel; 15. Filter media layer. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0019] The following specific embodiments illustrate the implementation manners 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.

[0020] Now, exemplary embodiments of the present invention are introduced with reference to the accompanying drawings. 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 relevant art. The terms in the exemplary embodiments shown in the drawings are not limitations on the present invention. In the drawings, the same units / components are denoted by the same reference numerals.

[0021] Unless otherwise specified, the terms (including scientific and technical terms) used herein have the ordinary meaning understood by those skilled in the relevant art. Additionally, it can be understood that terms defined in a commonly used dictionary should be understood as having a meaning consistent with the context of their relevant fields, and should not be understood as having an idealized or overly formal meaning.

[0022] Embodiment 1 This embodiment provides an oilfield produced water filtration device, as Figure 1 shown, which includes an enhanced oil removal unit 7, a primary filtration unit 1, and a secondary filtration unit 2. The water outlet of the enhanced oil removal unit 7 is connected to the primary filtration unit 1, and the primary filtration unit 1 is connected to the secondary filtration unit 2 through a water outlet pipeline 4. For this oilfield produced water filtration device provided by the present invention, by setting an enhanced oil removal unit 7 in front of the primary filtration unit 1, the oil in the filtration medium is effectively removed and treated. The treated produced water then enters the filter for subsequent disposal, solving problems such as frequent filtration pollution during the operation of conventional filters, difficult backwashing of the filter after being contaminated, incomplete backwashing, and decline in the filtration capacity of the filter media.

[0023] Embodiment 2 Based on Embodiment 1, this embodiment provides an oilfield produced water filtration device, as Figure 2 shown. The enhanced oil removal unit 7 includes a conical oil removal funnel and a swirl flow channel 14. The swirl flow channel 14 is arranged on the inner wall of the conical oil removal funnel. The top of the conical oil removal funnel is connected to an oil collection pipeline 8, and the upper side of the conical oil removal funnel is connected to a water inlet pipeline 3.

[0024] As Figure 3 shown, the swirl flow channel 14 is a structure that spirals downward. Through the guidance of the flow channel, a rotational flow of the conveying medium is formed, and then a centrifugal swirl operation is formed. Separation is achieved due to the density difference under the action of centrifugal force.

[0025] Working principle: The produced water tangentially enters the conical oil removal funnel through the water inlet pipeline 3. Through the internally arranged swirl flow channel 14, the water is guided into the interior of the conical oil removal funnel to form a swirl flow pattern. During the swirl flow process, due to the different gravity of oil and water, under the action of centrifugal force, the oil in the water moves in the center of the swirl and gradually downward. Because the bottom of the conical oil removal funnel becomes narrower, a reverse flow is formed, and the oil in the swirl center moves upward. Finally, it enters the top of the conical oil removal funnel, and the separated oil is recovered through the oil collection pipeline 8 and removed from the water treatment system to achieve oil removal.

[0026] Embodiment 3 Based on Embodiment 1, this embodiment provides an oilfield produced water filtration device. Filter media layers 15 are filled in the middle of both the primary filtration unit 1 and the secondary filtration unit 2. The lower end of the enhanced oil removal unit 7 is arranged inside the primary filtration unit and above the filter media layer 15.

[0027] After being deoiled by the enhanced deoiling unit 7, the separated water moves downward and enters the intermediate filter media layer 15 of the primary filtration unit 1 through the bottom outlet of the conical deoiling funnel. After primary filtration, the produced water enters the secondary filtration unit 2 for further filtration, and the secondary filtered water enters the purified water tank for storage and reinjection.

[0028] Example 4 Based on Example 2, this example provides an oilfield produced water filtration device. As Figure 1 shown, the bottom end of the conical deoiling funnel is connected to a uniform water distribution device 9, and the uniform water distribution device 9 uses a conical screen plate.

[0029] The water separated from the outer periphery of the cyclone moves downward and enters the intermediate filter layer through the bottom outlet of the conical deoiling funnel. To make the water outlet of the conical deoiling funnel more uniform, a uniform water distribution device 9 is provided in the conical deoiling funnel. This device uses a screen plate. Through the interception of the screen plate and water distribution through the screen holes, uniform distribution of the water outlet is achieved, and it passes through the intermediate filter media layer 15 of the primary filtration unit 1 evenly and stably.

[0030] Example 5 Based on Example 1, this example provides an oilfield produced water filtration device. The bottom of the primary filtration unit 1 is connected to a first backwash inlet pipeline 5, and the upper part of the primary filtration unit 1 is connected to a first backwash sewage pipeline 6; the bottom of the secondary filtration unit 2 is connected to a second backwash inlet pipeline 11, and the upper part of the secondary filtration unit 2 is connected to a second backwash sewage pipeline 12.

[0031] As Figure 1 shown, when it is necessary to clean the primary filtration unit 1 and the secondary filtration unit 2 after running for a period of time, the first backwash inlet pipeline 5 and the second backwash inlet pipeline 11 are respectively connected to the purified water tank for backwashing, and the backwash water is discharged through the first backwash sewage pipeline 6 and the second backwash sewage pipeline 12 respectively.

[0032] Example 6 Based on Example 2, this example provides an oilfield produced water filtration device. An oil discharge valve is provided on the oil collection pipeline 8, and a viewing window is provided on the conical deoiling funnel.

[0033] During the filtration process, it is under pressure. The oil formed by cyclone separation coalesces at the top of the conical deoiling funnel, and the oil collection control can be achieved through the viewing window. Open the oil discharge valve for oil collection operation.

[0034] A coalescing oil removal pipe 13 is provided between the water inlet pipeline 3 and the conical deoiling funnel. The coalescing oil removal pipe 13 is filled with coalescing packing, and flow channels are provided in the coalescing packing.

[0035] As Figure 2As shown, the diameter of the coalescing oil removal pipe 13 is the same as that of the water inlet pipe. The water inlet pipe is filled with cylindrical coalescing fillers. There are flow channels and structures inside the coalescing fillers. Through the coalescing structure, the oil content in the water increases from small to large, forming coalescence.

[0036] Embodiment 7 This embodiment provides a method for filtering produced water in oil fields. After the produced water is deoiled by a settling oil removal tank, it enters the enhanced oil removal unit 7 through the water inlet pipeline 3. After enhanced oil removal, it enters the primary filtration unit 1 and is subjected to primary filtration through the filter media layer 15. After primary filtration, the produced water enters the secondary filtration unit 2 for secondary filtration. The secondary filtration effluent enters the purified water tank through the drainage pipeline 10 for storage and reinjection.

[0037] The specific process of enhanced oil removal is as follows: The produced water tangentially enters the conical oil removal funnel through the water inlet pipeline 3, and under the guidance of the swirl flow channel 14, a swirl flow pattern is formed inside the conical oil removal funnel. During the swirl flow process, due to the different gravities of oil and water, under the action of centrifugal force, the oil content in the water moves in the center of the swirl and gradually downward. Since the bottom of the conical oil removal funnel becomes narrower, a reverse flow is formed, and the oil content moves upward in the center of the swirl. Finally, it enters the top of the conical oil removal funnel, and finally, the separated oil content is recovered through the oil collection pipeline 8 and removed from the water treatment system to achieve enhanced oil removal.

[0038] When it is necessary to clean the primary filtration unit 1 and the secondary filtration unit 2 after running for a period of time, the backwash water inlet pipeline one 5 and the backwash water inlet pipeline two 11 are respectively connected to the purified water tank for backwashing, and the backwash water is discharged through the backwash sewage pipeline one 6 and the backwash sewage pipeline two 12 respectively.

[0039] In the present invention, an enhanced oil removal unit 7 is provided in front of the primary filtration unit 1. The produced water tangentially enters the conical oil removal funnel of the enhanced oil removal unit 7 through the water inlet pipeline 3. Through the internally arranged swirl flow channel 14, the water is guided into the interior of the conical oil removal funnel to form a swirl flow pattern. During the swirl flow process, due to the different gravity of oil and water, under the action of centrifugal force, the oil in the water runs in the center of the swirl and gradually moves downward. Since the bottom of the conical oil removal funnel becomes narrower, a reverse flow is formed, and the oil in the center of the swirl moves upward, finally entering the top of the conical oil removal funnel. Then, the separated oil is recovered through the oil collection pipeline 8 and removed from the water treatment system to achieve re-oil removal; the water separated from the outer periphery of the swirl moves downward and enters the intermediate filtration layer through the bottom outlet of the conical oil removal funnel. To make the water outlet of the conical oil removal funnel more uniform, a uniform water distribution device 9 is arranged in the conical oil removal funnel. This device uses a screen folded plate to achieve uniform distribution of the water outlet and smoothly pass through the bottom filtration layer. The upgrade and transformation of the filter enable the treatment function of the filter to be upgraded from the original simple filtration and interception function to a composite function of coalescing oil removal, swirl oil removal, pressure oil collection, and filtration. The proprietary structure of coalescing swirl oil removal and pressure oil collection realizes the improvement of the oil removal capacity in the front stage, weakens the influence of upstream oil content fluctuations on the filter, broadens the conditions of the inlet water quality of the filter, improves the adaptability of the filter, and extends the service life of the filter.

[0040] The method of the present invention first performs enhanced oil removal and then filtration. Generally, the requirements for the inlet water quality of filtration are: oil content ≤ 50 mg / L, suspended solid content ≤ 60 mg / L, while the present invention can further improve the water quality indicators at the inlet of the filter: oil content ≤ 80 - 100 mg / L, suspended solid content ≤ 80 - 100 mg / L. The requirements for the inlet water quality are reduced, the water quality range that the filter adapts to in the front stage is broadened. Compared with the conventional filter under the same conditions, the filtration treatment load is reduced, the frequency of the filter being contaminated by dirty oil and the number of backwashing are decreased, the water outlet quality of the filter is improved, and at the same time, the further recovery and utilization of the dirty oil in the produced water are realized.

[0041] 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 filtration device, characterized in that: It includes a strengthened oil removal unit, a primary filtration unit and a secondary filtration unit. The water outlet of the strengthened oil removal unit is communicated with the primary filtration unit, and the primary filtration unit is communicated with the secondary filtration unit through a water outlet pipeline.

2. The oilfield produced water filtration device according to claim 1, characterized in that: The strengthened oil removal unit includes a conical oil removal funnel and a swirl flow channel. The swirl flow channel is arranged on the inner wall of the conical oil removal funnel. An oil collection pipeline is communicated with the top of the conical oil removal funnel, and a water inlet pipeline is communicated with the upper side of the conical oil removal funnel.

3. The oilfield produced water filtration device according to claim 1, characterized in that: Filter media layers are filled in the middle of both the primary filtration unit and the secondary filtration unit. The lower end of the strengthened oil removal unit is arranged in the primary filtration unit and above the filter media layer.

4. The oilfield produced water filtration device according to claim 2, characterized in that: A uniform water distribution device is communicated with the bottom end of the conical oil removal funnel. The uniform water distribution device adopts a conical screen folded plate.

5. The oilfield produced water filtration device according to claim 1, characterized in that: A backwash water inlet pipeline 1 is communicated with the bottom of the primary filtration unit, and a backwash sewage discharge pipeline 1 is communicated with the upper part of the primary filtration unit; a backwash water inlet pipeline 2 is communicated with the bottom of the secondary filtration unit, and a backwash sewage discharge pipeline 2 is communicated with the upper part of the secondary filtration unit.

6. The oilfield produced water filtration device according to claim 2, characterized in that: An oil discharge valve is arranged on the oil collection pipeline, and a viewing window is arranged on the conical oil removal funnel.

7. The oilfield produced water filtration device according to claim 2, characterized in that: A coalescing oil removal pipe is arranged between the water inlet pipeline and the conical oil removal funnel. The coalescing oil removal pipe is filled with coalescing packing, and a flow channel is arranged in the coalescing packing.

8. An oilfield produced water filtration method, using the oilfield produced water filtration device according to claim 2, characterized in that: The produced water is deoiled by a settling oil removal tank and then enters the strengthened oil removal unit through the water inlet pipeline. After strengthened oil removal, it enters the primary filtration unit and is primarily filtered through the filter media layer. After primary filtration, the produced water enters the secondary filtration unit for secondary filtration. The secondary filtered water enters the purified water tank through the drainage pipeline for storage and reinjection.

9. The oilfield produced water filtration method according to claim 8, characterized in that: The specific process of strengthened oil removal is as follows: The produced water tangentially enters the conical oil removal funnel through the water inlet pipeline and forms a swirl flow pattern inside the conical oil removal funnel under the guidance of the swirl flow channel. During the swirl flow process, due to the different gravity of oil and water, under the action of centrifugal force, the oil in the water runs in the center of the swirl and gradually moves downward. Since the bottom of the conical oil removal funnel becomes narrower, a reverse flow is formed, and the oil in the center of the swirl moves upward, finally entering the top of the conical oil removal funnel. Finally, the separated oil is recovered through the oil collection pipeline and removed from the water treatment system to achieve strengthened oil removal.

10. The oilfield produced water filtration method according to claim 8, characterized in that: When it is necessary to clean the primary filtration unit and the secondary filtration unit after running for a period of time, the backwash water inlet pipeline 1 and the backwash water inlet pipeline 2 are respectively connected to the purified water tank for backwashing, and the backwash water is discharged through the backwash sewage pipeline 1 and the backwash sewage pipeline 2 respectively.

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