Chemical flooding oil production wastewater treatment system for oil field

Abstract

The utility model relates to the technical field of oil field wastewater treatment, and provides an oil field chemical flooding oil production wastewater treatment system which comprises a first-stage air flotation machine (2), a second-stage air flotation machine (3), a feeding pump (5), a filter (6) and a water purification tank (7) which are sequentially connected through a pipeline, the first-stage air flotation machine (2) is connected with an ozone generator, the second-stage air flotation machine (3) is connected with a dosing device (10), and the top of the first-stage air flotation machine (2), the top of the second-stage air flotation machine (3), the bottom of the first-stage air flotation machine (2) and the bottom of the second-stage air flotation machine (3) are all connected with a sludge tank (11). The oilfield chemical flooding oil extraction wastewater treatment system has the characteristics of advanced process, stable operation, high treatment efficiency, low operation cost and the like when being used for treating oilfield chemical flooding oil extraction wastewater, and meets the requirement of reinjection after oilfield chemical flooding produced water is treated to reach the standard.

Description

Technical Field

[0001] This application belongs to the field of oilfield wastewater technology, and more specifically, relates to an oilfield chemical flooding wastewater treatment system. Background Technology

[0002] Oilfield integrated stations are a crucial processing stage in oil extraction, with main functions including crude oil dehydration, oil-gas separation, crude oil stabilization, wastewater treatment, and water injection. Wastewater treatment primarily addresses wastewater generated during oilfield production to ensure it meets relevant standards.

[0003] With the continuous development of oilfields and the widespread adoption of chemical flooding technology, the composition of wastewater treated by oilfield joint stations has become increasingly complex. This is mainly manifested in the high degree of emulsification of wastewater, which increases the difficulty of oil-water separation. In addition, the wastewater contains a high amount of macromolecular polymers, which increases the viscosity of the wastewater and makes it difficult to degrade.

[0004] Currently, the traditional wastewater treatment process at oilfield joint stations involves two-stage sedimentation and two-stage filtration. This process suffers from problems such as outdated technology, high operating costs, and large fluctuations in the quality of the discharged water. Furthermore, there is a risk that substandard water quality may lead to reinjection, which in turn could affect the formation structure and the recovery rate of crude oil.

[0005] Therefore, developing new technologies to upgrade existing processes is imperative to address the above challenges. The efficient operation of oilfield joint stations is of great significance for improving overall oilfield production efficiency and ensuring crude oil quality. Utility Model Content

[0006] To address the shortcomings of the existing technology, the purpose of this application is to provide an oilfield chemical flooding wastewater treatment system, which features advanced technology, stable operation, high treatment efficiency, and low operating costs, and meets the requirements for reinjection of oilfield chemical flooding produced water after treatment to meet standards.

[0007] To achieve the above objectives, the technical solution adopted in this application is as follows: An oilfield chemical flooding wastewater treatment system is provided, comprising: a primary air flotation unit, a secondary air flotation unit, a feed pump, a filter, and a clean water tank connected sequentially via pipelines; the primary air flotation unit is connected to an ozone generator, the secondary air flotation unit is connected to a dosing device, and the top of the primary air flotation unit, the top of the secondary air flotation unit, the bottom of the primary air flotation unit, and the bottom of the secondary air flotation unit are all connected to a sludge tank.

[0008] In one embodiment, the inlet pipe of the primary air flotation unit is connected to the booster pump, and a pipe mixer is provided on the inlet pipe. The ozone generator is connected to the inlet pipe and the connection position is located at the front end of the pipe mixer.

[0009] In one embodiment, the ozone generator is an electrolyzed water ozone generator.

[0010] In one embodiment, the dosing device includes a dosing tank, a pressure pump, a flow meter, and an injector.

[0011] In one embodiment, a buffer tank is provided between the secondary air flotation unit and the feed pump, and the bottom of the buffer tank is connected to the sludge tank.

[0012] In one embodiment, the filter is a rotary bed filter with at least four layers of filter media inside, each layer of filter media being modified glass particles with decreasing size from top to bottom.

[0013] In one embodiment, the purified water tank is connected to a water injection station.

[0014] In one embodiment, the sludge tank is connected to a screw pump and a sludge thickener.

[0015] In one embodiment, the sludge thickener is a screw press.

[0016] The beneficial effects of the oilfield chemical flooding wastewater treatment system provided in this application are as follows:

[0017] 1. A new ozone generator was added. The ozone it produces is mixed with the wastewater from chemical flooding and undergoes an oxidation reaction, which can reduce the proportion of long molecular chains. At the same time, it also has a demulsification function. After the viscosity of the polymer-containing wastewater is reduced, the collision probability of water sample oil droplets is increased, the particle size of water sample oil droplets increases, the oil droplets aggregate and float to the surface, and the oil-water separation effect is obvious.

[0018] 2. The production process utilizes a two-stage air flotation unit connected in series. The first-stage air flotation unit is responsible for demulsification, viscosity reduction, and separation of most of the floating oil, with a residence time of 30-45 minutes. The second-stage air flotation unit is responsible for chemical addition, coagulation, and coagulation assistance. After flocs are formed, they float to the surface with microbubbles, separating the scum, with a residence time of 45-60 minutes. The two-stage air flotation unit connected in series can more effectively remove oil and suspended solids, and can greatly reduce the operating load of the downstream filter.

[0019] 3. The primary air flotation unit does not require the addition of any chemical agents. It uses ozone to demulsify and reduce viscosity of wastewater in advance. The amount of chemicals added to the secondary air flotation unit can be reduced by 12-18% compared with the traditional process, which greatly reduces operating costs.

[0020] 4. The filter uses a vortex bed filter with four different sizes of modified glass particles as the filter media. The specially treated glass filter media achieves optimal particle size and shape, and then undergoes chemical activation treatment to increase the surface area to more than 300 times that of broken glass or sand particles. This allows the vortex bed filter to achieve a suspended solids removal rate of 90-97%, with a removal precision as low as 0.45µm. The filtration flow rate of the vortex bed filter is 4-5 times that of traditional sand filters, and the processing capacity of a filter tank of the same size can reach 3-5 times that of a traditional sand filter. The equipment also features a small footprint, low backwash water consumption, and low power load.

[0021] 5. This oilfield chemical flooding wastewater treatment system can be manufactured as a skid-mounted unit, directly drawing water from the two-stage settling tanks in the original system of the oilfield joint station and connecting it to the inlet of the chemical flooding wastewater treatment system. After treatment by the system, the treated water meets the standards and can be directly used for oilfield reinjection. It features advanced technology, stable compliance with standards, and low operating costs, making it more practical and economical. Attached Figure Description

[0022] To more clearly illustrate the technical solutions in the embodiments of this application, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0023] Figure 1 This is an exploded structural diagram of an oilfield chemical flooding wastewater treatment system provided in an embodiment of this application.

[0024] The following are the labeling elements in the figure:

[0025] 1. Booster pump; 2. Primary air flotation unit; 3. Secondary air flotation unit; 4. Buffer tank; 5. Feed pump; 6. Filter; 7. Clean water tank; 8. Electrolyzed water ozone generator; 9. Pipeline mixer; 10. Dosing device; 11. Sludge tank; 12. Screw pump; 13. Sludge thickener. Detailed Implementation

[0026] To make the technical problems, technical solutions, and beneficial effects to be solved by this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and are not intended to limit the scope of this application.

[0027] It should be noted that when a component is referred to as being "fixed to" or "set on" another component, it can be directly on or indirectly on that other component. When a component is referred to as being "connected to" another component, it can be directly connected to or indirectly connected to that other component.

[0028] It should be understood that the terms "length", "width", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this application.

[0029] Furthermore, 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 technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this application, "multiple" means two or more, unless otherwise explicitly specified.

[0030] like Figure 1 As shown in the illustration, an oilfield chemical flooding wastewater treatment system provided in this application embodiment will now be described. This oilfield chemical flooding wastewater treatment system includes: a primary air flotation unit 2, a secondary air flotation unit 3, a buffer tank 4, a feed pump 5, a filter 6, and a clean water tank 7, all connected sequentially via pipelines. The primary air flotation unit 2 is connected to an ozone generator, and its inlet pipe is connected to a booster pump 1. Wastewater is pumped into the primary air flotation unit 2 via the booster pump 1. A pipe mixer 9 is installed on the inlet pipe, and the ozone generator is connected to the inlet pipe at the front end of the pipe mixer 9. Thus, the ozone generated by the ozone generator mixes evenly with the wastewater after passing through the pipe mixer 9, achieving the demulsification, viscosity reduction, and separation of most of the floating oil by the primary air flotation unit 2. The secondary air flotation unit 3 is connected to a dosing device 10, used for chemical dosing and coagulation within the secondary air flotation unit 3, forming flocs that float to the surface with microbubbles, thus separating scum. In this embodiment, the top of the primary air flotation unit 2, the top of the secondary air flotation unit 3, the bottom of the primary air flotation unit 2, the bottom of the secondary air flotation unit 3, and the bottom of the buffer tank 4 are all connected to the sludge tank 11 to discharge floating oil, scum, and sediment into the sludge tank 11. The sludge tank 11 is connected to the screw pump 12 and the sludge thickener 13. The screw pump 12 is used to pump sludge into the sludge thickener 13, and the sludge thickener 13 dewaters the sludge.

[0031] Preferably, the ozone generator is an electrolytic water ozone generator 8; thus, the amount of ozone generated by the electrolytic water ozone generator 8 can be frequency-controlled by the number of start-up modules, matching the operation with the wastewater treatment volume and the polymer content in the wastewater. The dosing device 10 includes a dosing tank, a pressurizing pump, a flow meter, and an injector; the injector is connected to the pipeline between the primary flotation unit 2 and the secondary flotation unit 3. The pressurizing pump is used to transport the reagents in the dosing tank and spray them into the pipeline through the injector to better mix the reagents with the wastewater. The flow meter is used to measure the dosage of the reagents. The reagents in the dosing tank are PAC and PAM.

[0032] Preferably, filter 6 is an existing rotary bed filter containing at least four layers of filter media, each layer consisting of modified glass particles with decreasing size from top to bottom. The filter media uses four different sizes of modified glass particles, which undergo special treatment to achieve optimal particle size and shape. These particles are then chemically activated to increase their surface area to more than 300 times that of broken glass or sand. The clean water tank 7 is connected to the water injection station for water reinjection into the oilfield. The sludge thickener 13 is a screw press; the sludge exiting the screw press has a moisture content not exceeding 95% before being transported to a sludge treatment plant for further processing.

[0033] In this embodiment, wastewater from the outlets of the two-stage settling tanks within the oilfield joint station is pressurized to 0.15-0.2 MPa by booster pump 1. Before being discharged into the primary air flotation unit 2, the wastewater is thoroughly mixed with ozone generated by the electrolytic water ozone generator 8 through a pipeline mixer 9, resulting in an oxidation reaction that demulsifies and reduces viscosity of the chemical flooding wastewater, thereby enhancing the oil-water separation effect. The residence time of the chemical flooding wastewater in the primary air flotation unit 2 is 30-45 minutes. Simultaneously, the top scraper of the primary air flotation unit 2 is activated to scrape off the floating oil on top of the primary air flotation unit 2 and periodically discharge the sludge from the bottom of the primary air flotation unit 2 into the sludge tank 11.

[0034] In this embodiment, the dosing device 10 adds 5% PAC and 0.1-0.5% PAM. The secondary air flotation unit 3 performs the dosing, coagulation, and flocculation aid processes, forming flocs that float to the surface with microbubbles, separating scum. The residence time is 45-60 minutes. The top scum and bottom sludge of the secondary air flotation unit 3 are periodically discharged into the sludge tank 11.

[0035] A feed pump 5 is installed before the filter 6. The outlet delivery pressure of the feed pump 5 is about 0.3MPa. It is used to pump the oilfield wastewater in the buffer tank 4 into the filter 6. The filter media in the filter 6 is modified glass particles of four different sizes, which makes the vortex filter 6 have a suspended solids removal rate of up to 90-97% and a suspended solids removal precision as low as 0.45µm. After the filtered oilfield wastewater meets the standards, it is discharged into the clean water tank 7.

[0036] Wastewater generated by sludge thickener 13 is returned to the primary air flotation unit 2 for recycling. After the wastewater from chemical flooding is treated to meet standards, it is transported from clean water tank 7 to the water injection station for oilfield reinjection.

[0037] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A wastewater treatment system for chemical flooding in oilfields, characterized in that, include: The primary air flotation unit (2), the secondary air flotation unit (3), the feed pump (5), the filter (6), and the clean water tank (7) are connected in sequence by pipelines; the primary air flotation unit (2) is connected to an ozone generator, the secondary air flotation unit (3) is connected to a dosing device (10), and the top of the primary air flotation unit (2), the top of the secondary air flotation unit (3), the bottom of the primary air flotation unit (2), and the bottom of the secondary air flotation unit (3) are all connected to the sludge tank (11).

2. The oilfield chemical flooding wastewater treatment system as described in claim 1, characterized in that: The inlet pipe of the first-stage air flotation machine (2) is connected to the booster pump (1). A pipe mixer (9) is provided on the inlet pipe. The ozone generator is connected to the inlet pipe and the connection position is located at the front end of the pipe mixer (9).

3. The oilfield chemical flooding wastewater treatment system as described in claim 2, characterized in that: The ozone generator is an electrolytic water ozone generator (8).

4. The oilfield chemical flooding wastewater treatment system as described in claim 3, characterized in that: The dosing device (10) includes a dosing tank, a pressure pump, a flow meter, and an injector.

5. The oilfield chemical flooding wastewater treatment system as described in claim 4, characterized in that: A buffer tank (4) is also provided between the secondary air flotation machine (3) and the feed pump (5), and the bottom of the buffer tank (4) is connected to the sludge tank (11).

6. The oilfield chemical flooding wastewater treatment system as described in any one of claims 1-5, characterized in that: The filter (6) is a rotary bed filter, which has at least four layers of filter media inside. Each layer of filter media is a modified glass particle with a size that decreases from top to bottom.

7. The oilfield chemical flooding wastewater treatment system as described in claim 6, characterized in that: The purified water tank (7) is connected to the water injection station.

8. The oilfield chemical flooding wastewater treatment system as described in claim 7, characterized in that: The sludge tank (11) is connected to a screw pump (12) and a sludge thickener (13).

9. The oilfield chemical flooding wastewater treatment system as described in claim 8, characterized in that: The sludge thickener (13) is a screw press.

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