KR20200031832A - Produced water treatment system - Google Patents

Abstract

The present invention relates to a production water treatment system for finally separating oil contained in production water generated in an oil production process from the production water. More specifically, the present invention is provided to make up for the shortage of production water in order to prevent the degradation of the performance of hydrocyclone for separating oil in the production water from the production water. The production water treatment system according to the present invention for achieving the above includes: a surge container which stores production water generated from a well; a hydrocyclone which primarily separates the oil in the production water through centrifugation of the product water supplied from the surge container; a gas floating separator which finally separates fine oil particles by using gas from the primarily separated production water; a production water drainage line which drains production water separated from the gas floating separator; and an oil and water separation fluid recovery line which branches from the production water drainage line and supplies the production water to the surge container. The present invention has technical characteristics of compensating for production water treated through an oil and water separation fluid recovery line when the amount of the production water flowing into hydrocyclone is smaller than the proper inflow amount of production water.

Description

Produced water treatment system

The present invention relates to a production water treatment system for finally separating the oil contained in the production water from the production water generated in the process of oil production, in particular to prevent the degradation of the performance of the hydrocyclone to separate the oil in the production water from the production water In order to do so, it was configured to make up for the shortage of water.

Produced Water is Oily Wastewater, which accounts for the largest portion of waste generated during the oil production process, and is essentially water trapped in groundwater discharged to the surface during oil production. In general, the amount of oil production varies slightly depending on the characteristics of the oil well and the operation period, but generally, the number of productions for producing one barrel of oil is about 7 to 10 barrels. These products are very toxic and usually contain oil, grease and other hydrocarbons, as well as large amounts of salts, metals and trace elements. Managing this can have a significant environmental impact and can be costly.

The petroleum component extracted from the oil sands is a heavy, sticky black viscous oil called bitumen, which accounts for about 10 to 12% of the oil sands. Conventional crude oil is lighter than water, but since bitumen has a specific gravity similar to water, the bitumen does not flow in boreholes or oil pipelines in natural conditions, so steam is added or diluents (ultra-light crude oil or light petroleum products) are used. It is obtained by mixing and lowering the specific gravity and viscosity, and then transporting it to the oil pipeline. Therefore, in order to recover oil, bitumen contains a large amount of water, so the primary separation FWKO (Free Water Knock-Out), the secondary separation by using anti-emulsifiers (Demulsifier Chemicals), electric field (Electrostatic Field), etc. To recover. The production water generated after the recovery of the oil component still contains a large amount of oil and solid solutions, etc. In order to discharge or recycle it, it must be processed through a production water treatment process that treats it with water containing 15 ppm or less of oil before it can be drained to the sea.

The production water treatment methods are classified into three types, physical treatment methods, biological treatment methods, and chemical treatment methods. The most commonly used method is a physical treatment method, and a method having high separation efficiency is a biological treatment method and a chemical treatment method.

Physical treatment is the most easy to use method: Filtration, Sorption, Gravity, Centrifugal force, Membrane, Distillation, Skimmer, Suspension There are many treatment methods such as (Flotation). The advantage is that it is easier to control than the chemical treatment technology or biological treatment technology, and the disadvantage is that it is difficult to expect high separation efficiency with the physical processing technology.

In order to reliably remove the organic substances contained in the product water, methods using chemical reactions or biological reactions are additionally required. The most commonly used technologies are filtration and sorption (adsorption / absorption) and gravity sedimentation. Filtration and sorption have the advantage that the material can be easily obtained, and gravity sedimentation has the advantage that the device drying cost is more expensive than filtration or sorption, but it requires less maintenance.

The biological treatment method can be classified into a treatment method using microorganisms and a treatment method using activated sludge. The treatment method by microorganisms can be divided into aerobic microbial methods and anaerobic microbial methods. Among biological treatment methods, aerobic microbial treatment is the most commonly used, and there are trickling filters, sequencing batch reactors (SBR), and biological aerated filters. The method of treatment by anaerobic microorganisms has the advantage of high cost-effectiveness when used when the concentration of contaminants is low. The reed bed method is widely used and shows an average of 96% hydrocarbon separation efficiency at 3,000 m3 / day production water treatment.

Activated sludge is a type of aerobic microbial method and is one of the most used technologies in water treatment processes. It is mainly used with skimmer technology, and is known to exhibit a separation efficiency of about 98 to 99% at a solids retention time (SRT) of 20 days.

Chemical treatment methods include oxidation, coagulation, and demulsifier chemicals. Recently, electrochemical processes and photocatalytic treatments have been used. Research is ongoing.

The oxidation method is mainly used as a method for decomposing refractory chemicals, and uses strong oxidants, catalysts, and irradiation. Currently, the technology called Advanced Oxidation Process (AOP) has been developed and commercialized, and AOP generates a large amount of OH radicals in the process of photolysis by combining with oxygen in the air by simultaneously generating ultraviolet wavelength and ozone generating wavelength in the discharge lamp. It is a process of generating and oxidizing. Condensation is mainly used to remove suspended solids or colloidal particles, and is inefficient for removing dissolved substances.

In the drawings, Figure 1 is a conceptual diagram showing a production water treatment system according to the prior art.

As shown in FIG. 1, a produced water treatment system (PWTS) is a surge vessel 10 in which the introduced product water is stored and a pressure inside the surge vessel 10. The fuel gas line 11 for supplying the fuel gas to the hazard, the vent line 13 for discharging the fuel gas from the surge vessel 10, and the production water stored in the surge vessel 10 are supplied and oil in the production water by centrifugal force The hydrocyclone 20 for primary separation, and the oil recovery line 21 extending from the hydrocyclone 20 to the oil system to re-feed the separated oil to the oil system, and the oil A gas floatation unit (GFU) 30 for final separation of fine oil particles from production water by using gas from the separated production water, the production water finally processed in the gas floating separator 30 is Through the production drainage line (31) Drained into the ocean.

In a conventional production water treatment system, the production water introduced into the hydrocyclone 20 is centrifugally rotated based on the pressure of the surge vessel 10 held by the fuel gas, and oil and production water are generated by the centrifugal force generated. Is separated.

The hydrocyclone 20 configured as described above is equipped with a large amount of a liner in line with a required flow rate therein, and the performance of oil-water separation includes the production water flowing into the hydrocyclone 20 and the oil recovery line 21. By controlling the pressure difference ratio and the pressure difference ratio between the pressure difference and the product water primaryly separated from the hydrocyclone 20, the oil separation performance of the hydrocyclone 20 is controlled.

On the other hand, in the case of offshore oil wells, the components of the production water introduced over time are different and it is difficult to stably receive the production water due to the surging of the pipeline. That is, since the flow rate of the production water is not uniform, the control of the differential pressure ratio is not smooth, and the performance of separating the oil from the hydrocyclone is deteriorated.

In general, as the liner inside the hydrocyclone is installed in accordance with the maximum flow rate of the production water, when the flow rate of the production water decreases, the performance of the hydrocyclone occurs, and the number of line installations of the hydrocyclone is often adjusted according to the fluctuation of the flow rate. In order to do this, there is a disadvantage that equipment management is required.

More specifically, the PRV (Pressure ratio computation) 24 shown in FIG. 1 calculates the measured value of PDT1 (23a) and the measured value of PDT2 (23b) by Equation 1 below.

[Equation 1]

PRV = PDT2 / PDT1

Typically, the setting point of the pressure differential controller (PDC) is 1.8.

At this time, when the PRV value is greater than 1.8, the pressure differential control valve (PDCV) 25 is opened to stabilize the PDT2 by lowering it.

And if the PRV value is less than 1.8, the pressure differential control valve (PDCV) must be closed to increase PDT2 to stabilize it. If the amount of water flowing into the hydrocyclone is small, the PRV cannot be adjusted to 1.8 even if the PDCV is closed. The problem that the performance of the cyclone deteriorates occurs.

Republic of Korea Registered Patent Publication No. 10-1490147 (announcement date; 2015.02.05)

The present invention was invented to solve the problems of the prior art as described above, to provide a production water treatment system configured to improve the function of the hydrocyclone by keeping the amount of production water flowing into the hydrocyclone constant It has its purpose.

The production water treatment system according to the present invention for achieving the above object is a surge vessel for storing the product water generated in the oil well, and a hydro which primarily separates the oil from the product water by centrifuging the product water supplied from the surge container. Cyclone, a gas floating separator for final separation of fine oil particles using gas from the production water, a production water drainage line for draining the separated production water from the gas floating separator, and a final treated production branched from the production water drainage line It includes an oil-water separation fluid recovery line that re-supplies water to a surge container, and when the amount of production water flowing into the hydrocyclone is less than the proper production water inflow, compensation for the final processed water through the oil-water separation fluid recovery line Technical features.

In addition, according to a preferred embodiment of the present invention, the oil-water separation fluid recovery line is equipped with an ejector, and re-supplies the produced water finally processed to the surge vessel by powering the pressure of the fuel gas supplied through the fuel gas line connected to the ejector. do.

In addition, according to a preferred embodiment of the present invention, the oil-water separation fluid recovery line is equipped with a pressure differential control valve (PDCV), and when the pressure difference ratio of the hydrocyclone is less than or equal to a set point, the PDCV is opened to finalize it. The treated production water is supplied to a container.

In addition, according to a preferred embodiment of the present invention, a double backflow prevention valve is mounted between the branch and the discharger where the oil-water separation fluid recovery line is separated from the production water drainage line.

In addition, according to a preferred embodiment of the present invention, a fuel gas line is connected to the discharger, and when the fuel gas flowing into the discharger flows from the discharger to the surge vessel, the production water processed by the pressure of the fuel gas is transferred to the surge vessel. .

As described above, the production water treatment system according to the present invention supplements and supplies a portion of the product water that is separated by flowing water and drains into the hydrocyclone, thereby supplying the capacity of the liner installed inside the hydrocyclone. It has the advantage that it can improve the function of the hydrocyclone by maintaining a suitable flow rate.

In addition, by re-supplying the production water or the treated production water according to the capacity of the hydrocyclone liner, it is advantageous in that maintenance cost and time are not required due to replacement of the required liner when the production water flow rate is insufficient or high as in the prior art. There is this.

1 is a conceptual view showing a production water treatment system according to the prior art.
2 is a conceptual diagram showing a production water treatment system according to the present invention.

Hereinafter, a preferred embodiment of the production water treatment system according to the present invention will be described in detail with reference to the accompanying drawings.

In the drawings, Figure 2 is a conceptual diagram showing a production water treatment system according to the present invention.

As shown in FIG. 2, a produced water treatment system (PWTS) 100 includes a surge vessel 10 in which the introduced product water is stored and a pressure inside the surge vessel 10. In order to control the fuel gas line 11 for supplying fuel gas, the vent line 13 for discharging the fuel gas from the surge vessel 10, and the production water stored in the surge vessel 10 is supplied and flows by centrifugal force The hydrocyclone 20 to be separated, the oil recovery line 21 extending from the hydrocyclone 20 to the oil system to send the separated oil to the oil system, and the gas from the production water in which the oil is primarily separated are used. Gas floatation unit (GFU) 30 which finally separates the fine oil particles from the gas floating separator 30, so that the production water from which fuel gas is separated is drained from the gas floating separator 30. Drainage line (31) The oil-water separation fluid recovery line 120 branched from the water drainage line 31 is connected to the surge container 10, and the fuel gas line 11 is an ejector mounted on the oil-water separation fluid recovery line 120. It is connected to 110.

In this configuration, when the flow rate of the production water flowing into the hydrocyclone 20 from the production water treatment system 100 is small, through the oil-water separation fluid recovery line 120 to prevent deterioration of the performance of the hydrocyclone 20 It is configured to re-supply the final treated water to the surge container (10).

Hereinafter, the operational relationship of the production water treatment system configured as described above will be described in detail.

In the present invention, when the values transmitted from the PRV 24 to the PY1 and PY2 and the PDC2 125 through a pressure calculation loop are 1.6 or less, the fuel gas line PC 11a and the ventline PC 13a ) To maintain the opening degree of PCV1 and PCV2 at 10%, so that a certain amount of fuel gas flows into the discharger 110, PDCV2 is opened, and the production water drained through the production water drain line to the surge container 10 Start re-supply.

As described above, when the value of the PRV 24 is 1.8 or less, the inflow amount of the production water is considered to be an acceptable value or more than 1.6, and in the present invention, PY1 and PY2 and When the value transmitted to the PDC2 125 is 1.6 or less, operation starts.

When the fuel gas flows toward the discharger 110, the discharged water production line 31 through the oil and water separation fluid recovery line 120 by using the pressure of the fuel gas flowing into the discharger 110 and discharged to the surge container 10 as power After flowing the product water that is drained along the discharger 110, it is supplied to the surge container 10 together with fuel gas.

Therefore, when the inflow amount of the production water is small and the value transmitted from the PRV 24 to the PDC becomes 1.6 or less, the shortage amount of the production water flowing into the surge vessel 10 is resupplied to the surge vessel 10 for the final processed water. To supplement.

Here, the capacity of the discharger 110 should be equal to or larger than the minimum required flow rate for the normal performance of the hydrocyclone 20.

As described above, in the present invention, to prevent the degradation of the performance of the hydrocyclone 20 by supplementing the amount of the insufficient amount of the production water with the final treated production water to prevent the degradation of the performance of the hydrocyclone 20 due to the lack of inflow of the production water. It is possible to solve the difficulty in maintaining the inner liner of the hydrocyclone as in the prior art.

In addition, in the present invention, the oil-water separation fluid recovery line 120 is equipped with a double backflow prevention valve 121 for preventing the inflow of fuel gas between the discharger 110 and the PDCV2 (123).

100: production water treatment system
10: surge container
11: Fuel gas line
13: ventline
20: hydrocyclone
21: oil recovery line
30: gas floating separator
31: Production drainage line
110: ejector
120: Oil-water separation fluid recovery line
121: double backflow prevention valve
PDC: Pressure differential controller
PDCV: Pressure differential control valve
PDT: Pressure differential transmitter
PRV: Pressure ratio computation
LT: Level Transmitter
LC: Level Controller
PC: Pressure Controller
PT: Pressure Transmitter
LCV: Level Control Valve
PCV: Pressure Control Valve
SP: Set Point
MV: Mean Value
PV: Pressure Computation
PW: Produced Water

Claims (5)

Surge container for storing the production water from the well,
A hydrocyclone that centrifugally separates the product water supplied from the surge container into oil and product water,
Gas floating separator for separating fine oil particles using gas from the primary separated production water,
A production water drainage line for draining production water separated from the gas floating separator;
It includes an oil-water separation fluid recovery line that supplies the treated water branched from the production water drainage line to a surge container,
A production water treatment system characterized by compensating for the production water treated through an oil-water separation fluid recovery line when the amount of production water flowing into the hydrocyclone is less than the proper production water inflow.
According to claim 1,
The oil-water separation fluid recovery line is equipped with an discharger, and a production water treatment system characterized by supplying the production water treated by power of the pressure of the fuel gas supplied through the fuel gas line connected to the discharger to the surge vessel.
According to claim 2,
The oil-separated fluid recovery line is equipped with a pressure differential control valve (PDCV), and when the pressure difference ratio of the hydrocyclone is less than or equal to a set point, the PDCV is opened to re-supply the treated production water to the container. Production water treatment system.
According to claim 3,
A production water treatment system characterized in that a backflow prevention valve is installed between the branch and the discharger where the oil-water separation fluid recovery line is separated from the production water drainage line.
According to claim 4,
A fuel gas line is connected to the discharger, and when the fuel gas flowing into the discharger flows from the discharger to the surge vessel, the production water treatment system is characterized in that the production water is re-transmitted to the surge vessel by the pressure of the fuel gas.

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