Thickened oil produced water treatment process

Abstract

The invention belongs to the technical field of sewage treatment, and particularly relates to a heavy oil produced water treatment process. The thickened oil produced water treatment process comprises the following steps: S1, enabling thickened oil produced water to flow along an evaporation pipe in a film-forming manner from top to bottom, and heating the evaporation pipe, so that a water phase in the thickened oil produced water is evaporated into first water vapor; and S2, collecting the first water vapor, and carrying out purification treatment on the first water vapor. The heavy oil produced water can be treated, and the economic and environment-friendly effects are finally achieved.

Description

Technical Field

[0001] The present invention belongs to the technical field of sewage treatment, and specifically relates to a process for treating produced water from heavy oil production. Background Art

[0002] A large amount of wastewater generated from heavy oil thermal recovery in oilfields must be separated before it can be recycled. There are many methods for recycling, mainly membrane method and thermal method. These two methods are applied both at home and abroad. Relevant engineering examples have been partially applied in Canada, the United States, the United Kingdom, etc. However, since most oil production abroad is carried out in the low water cut period and the remaining amount of sewage is small, this technology has not been widely used in the oilfield field.

[0003] At the same time, there are also many problems in the adaptability and operation of the membrane method process and the conventional thermal method process for treating oilfield sewage. Therefore, it is necessary to optimize the treatment process and shorten the process flow.

[0004] The membrane method process refers to filtering water using a membrane made of special materials. The main disadvantages are as follows: 1. The requirement for the quality of influent water is high, and complex pretreatment processes are required for oilfield sewage to meet the requirements; 2. The service life of the membrane is short, and the membrane needs to be replaced every 3 - 5 years, with high costs and a large amount of maintenance work; 3. For oilfield sewage, the concentration multiple is low, and a large amount of concentrated water needs to be discharged; 4. It is extremely easy to be polluted. If the influent water quality does not meet the standard, it may cause membrane damage; 5. The reverse osmosis operating pressure is high, with a working pressure of 10 - 20 MPa and high energy consumption; 6. It is difficult to remove small molecule organic substances, and the effluent water quality is poor; 7. The temperature of oilfield sewage is relatively high, especially heavy oil sewage, and it needs to be cooled before membrane treatment.

[0005] The disadvantages of the conventional thermal method are as follows: 1. Forced circulation evaporation requires about 300 times the amount of circulating water, with high energy consumption and large equipment; 2. The multi-effect evaporation process requires a steam source. At the same time, the temperature difference is small, the heat transfer efficiency is low, the heat transfer area is large, the equipment volume is large, and the investment is high.

[0006] When the influent water is produced water from heavy oil production and it is required that the produced water can meet the boiler water demand, the present invention can shorten the process, extend the maintenance cycle, and ultimately achieve a more economical and environmentally friendly effect. Summary of the Invention

[0007] Aiming at the above-mentioned technical problems, the present invention aims to provide a process for treating produced water from heavy oil production, which can treat the produced water from heavy oil production and ultimately achieve an economical and environmentally friendly effect.

[0008] According to the present invention, there is provided a process for treating produced water from heavy oil production, including the following steps:

[0009] Step S1, allowing the produced water from heavy oil production to flow in a film along the evaporation tube from top to bottom, and heating the evaporation tube to evaporate the water phase in the produced water from heavy oil production into the first water vapor;

[0010] Step S2: Collect the first steam and purify it.

[0011] In a preferred embodiment, in step S1, the evaporation tube is heated by steam heating.

[0012] In a preferred embodiment, the first steam after being purified in step S2 is used to heat the evaporation tube.

[0013] In a preferred embodiment, after the first steam heats the evaporation tube, part of it enters the distilled water tank to form distilled water, and the other part exchanges heat with the heavy oil produced water.

[0014] In a preferred embodiment, the distilled water in the distilled water tank is used to exchange heat with the heavy oil produced water.

[0015] In a preferred embodiment, the first steam and part of the distilled water after heat exchange are discharged into a steam-water separation tank for steam-water separation, and the other part of the distilled water is directly discharged.

[0016] In a preferred embodiment, in step S1, before the heavy oil produced water enters the evaporation tube, oil removal treatment is performed.

[0017] In a preferred embodiment, a separation chamber is connected below the evaporation tube. The separation chamber is used to receive the heavy oil produced water to be treated and the heavy oil produced liquid after being treated by the evaporation tube. The lower end of the separation chamber is connected to the upper part of the evaporation tube through a circulation pump.

[0018] In a preferred embodiment, the heavy oil produced water to be treated is preheated before entering the separation chamber.

[0019] In a preferred embodiment, an oil removal device is provided between the lower end of the separation chamber and the upper end of the evaporation tube. The concentrated liquid formed after passing through the oil removal device is directly discharged.

[0020] Compared with the prior art, the advantages of the present application are as follows:

[0021] The present invention provides an evaporation tube, enabling the heavy oil produced water to flow in a film on the inner wall of the evaporation tube. At this time, heating the evaporation tube can have a very high evaporation capacity with extremely low energy consumption, low operating costs, and energy conservation and consumption reduction.

[0022] The steam produced by treating the heavy oil produced water in the present invention is used to heat the evaporation tube, which can reduce energy consumption. In addition, the steam produced by treating the heavy oil produced water in this method is also used for preheating the heavy oil produced water, further reducing energy consumption. Detailed implementation mode

[0023] In an embodiment of the present invention, a heavy oil produced water treatment process is provided, which is characterized by including the following steps: Step S1, making the heavy oil produced water flow in a film along the evaporation tube from top to bottom, and heating the evaporation tube to evaporate the water phase in the heavy oil produced water into the first water vapor; Step S2, collecting the first water vapor and performing purification treatment on it.

[0025] In a specific embodiment, the present invention also provides a treatment device for implementing the heavy oil produced water treatment process. The treatment device includes an evaporation chamber and a separation chamber arranged downstream of the evaporation chamber. The evaporation chamber specifically includes a housing and a plurality of evaporation tubes uniformly distributed inside the housing. The heavy oil produced water flows downward from top to bottom inside the evaporation tubes and forms a film on the inner wall of the evaporation tubes, thereby increasing the heating area of the heavy oil produced water and reducing energy consumption. After the heavy oil produced water passes through the evaporation tubes, it enters the separation chamber. In the separation chamber, the water phase in the heavy oil produced water becomes the first water vapor, which is discharged from the water vapor outlet of the separation chamber and enters the scrubbing tower for water vapor purification treatment.

[0026] According to the present invention, in step S1, the evaporation tube is heated by the method of water vapor heating.

[0027] Furthermore, the first water vapor after being purified by the step S2 is used to heat the evaporation tube. That is to say, after the first water vapor undergoes water vapor purification treatment in the scrubbing tower, it then enters the space between the housing and the evaporation tubes of the evaporation chamber, thereby realizing the recycling of heat and reducing energy consumption.

[0028] Furthermore, after the first water vapor heats the evaporation tube, part of it enters the distilled water tank to form distilled water, and the other part exchanges heat with the heavy oil produced water to be treated. In this embodiment, the heavy oil produced water to be treated passes through the separation chamber in the treatment device provided by the present invention. Before the heavy oil produced water to be treated enters the separation chamber, it first exchanges heat with the first water vapor to preheat and increase the temperature, thereby reducing energy consumption.

[0029] Furthermore, the present invention also uses the distilled water in the distilled water tank to exchange heat with the heavy oil produced water. Before the heavy oil produced water to be treated enters the separation chamber, it exchanges heat with the distilled water in the distilled water tank to preheat and increase the temperature, thereby reducing energy consumption.

[0030] Subsequently, the first water vapor and part of the distilled water after heat exchange are discharged into a steam-water separation tank for steam-water separation, and the other part of the distilled water is directly discharged.

[0031] In a preferred embodiment, in step S1, before the heavy oil produced water enters the evaporation tube, oil removal treatment is performed.

[0032] Specifically, the separation chamber of the present invention is used to receive the viscous oil produced water to be treated and the viscous oil produced liquid after being heated by the evaporation tube. The lower end of the separation chamber is connected above the evaporation tube through a circulation pump, and an oil removal device is provided between the lower end of the separation chamber and the upper end of the evaporation tube. The viscous oil produced water to be treated in the separation chamber passes through the oil removal device under the action of the circulation pump, and the oil removal device separates the oil phase in the viscous oil produced water. The concentrated liquid formed after the oil phase is separated by the oil removal device is directly discharged. After the oil phase in the viscous oil produced water is separated, the remaining part reaches above the evaporation chamber and then enters the evaporation tube, corresponding to step S1 above.

[0033] In a specific embodiment according to the present invention, the specific process flow of the viscous oil produced water treatment process is as follows.

[0034] The treatment device further includes a stock solution tank for storing the viscous oil produced liquid to be treated.

[0035] The stock solution tank and the separation chamber are connected by a pipeline, and the viscous oil produced water in the stock solution tank can enter the separation chamber through the pipeline. Two heat exchangers are also provided on the pipeline between the stock solution tank and the separation chamber. The water vapor after heating the evaporation tube and the distilled water in the distilled water tank are respectively connected to the two heat exchangers, and the water vapor after heating the evaporation tube is located downstream of the distilled water in the distilled water tank. That is to say, after the viscous oil produced water flows out of the stock solution tank, it is preheated by the water vapor and then preheated by the distilled water in sequence, and then enters the separation chamber.

[0036] Specifically, the viscous oil produced water in the stock solution tank enters the separation chamber from the side wall of the separation chamber.

[0037] In a specific embodiment, the temperature of the viscous oil produced water in the stock solution tank is 40 - 50 degrees Celsius, and the flow rate range of the viscous oil produced water flowing from the stock solution tank to the separation chamber is 2.5 - 3.5 m 3 / h. The temperature range of the viscous oil produced water after being preheated by the water vapor is 60 - 70 degrees Celsius, and the temperature range of the viscous oil produced water after being preheated by the distilled water is 75 - 85 degrees Celsius.

[0038] The bottom of the separation chamber is connected to the top of the evaporation chamber through a pipeline, and an oil removal device is also provided on the pipeline between the separation chamber and the evaporation chamber. The oil removal device can separate the oil phase in the viscous oil produced water. After the oil phase in the viscous oil produced water is separated, the concentrated liquid is discharged. The other fluids in the viscous oil produced water except the oil phase flow to the evaporation chamber, enter from the upper end of the evaporation chamber, and finally flow downwards in a film on the inner wall of the evaporation tube in the evaporation chamber. The film flow of the viscous oil produced water can increase the contact area, and only a small amount of heat is required to heat it.

[0039] In a specific embodiment, the temperature range at the bottom of the separation chamber is 70 to 80 degrees Celsius.

[0040] In a specific embodiment, the flow rate of the oil phase separated by the oil removal device is 0.3 to 0.5 m 3 / h.

[0041] Steam for heating the evaporation tubes is provided between the inside of the outer shell of the evaporation chamber and the outside of the evaporation tubes. In this embodiment, this part of the steam has two sources. One source is that the treatment device of the present invention is provided with a steam generator, which can continuously generate steam and introduce it into the inside from the outer shell of the evaporation chamber; the other source is the steam generated after the treatment device treats the viscous oil produced water. The steam generated by the treatment device treating the viscous oil produced water is also introduced into the inside from the outer shell of the evaporation chamber. Through this setting, using steam to heat the evaporation tubes can achieve rapid and uniform heating of the entire evaporation tubes. At the same time, it can make full use of energy and reduce energy consumption.

[0042] In a preferred embodiment, a first swirling device is arranged inside the evaporation tubes. The first swirling device can make the viscous oil produced water flowing in a film inside the evaporation tubes swirl, strengthening the scouring force on the inner wall of the evaporation tubes, preventing impurities from adhering to the inner wall of the evaporation tubes, reducing the cleaning of the inner wall of the evaporation tubes, and thus reducing the equipment maintenance funds.

[0043] After the viscous oil produced water is heated inside the evaporation tubes, it continues to flow downward and then enters the separation chamber. After the viscous oil produced water is heated, the water phase in it is evaporated to form steam. The treatment device provided by the present invention further includes a scrubbing tower. The scrubbing tower is connected to the side wall of the separation chamber through a pipeline. The steam in the separation chamber can enter the scrubbing tower along the pipeline. The scrubbing tower can purify the steam, thereby removing the impurities doped in the steam and making the purity of the steam reach the level that can be directly used as boiler water.

[0044] In a specific embodiment, the temperature range of the steam entering the scrubbing tower from the separation chamber is 85 to 95 degrees Celsius.

[0045] In a preferred embodiment, a second swirling device is arranged inside the separation chamber. After the viscous oil produced water flowing out of the evaporation tubes enters the separation chamber, it swirls under the action of the second swirling device, which can accelerate the evaporation of the water phase in the viscous oil produced water.

[0046] After the steam is purified by the scrubbing tower, a part of it is discharged back into the separation chamber to ensure that the temperature of the separation chamber is maintained at a specific level, and at the same time, it is beneficial for the viscous oil produced water in the separation chamber to evaporate to form new steam. Another part of the steam after being purified by the scrubbing tower enters the inside of the outer shell of the evaporation chamber through a pipeline, so as to heat the evaporation tubes.

[0047] In a preferred embodiment, a steam compressor is provided on the pipeline between the scrubbing tower and the evaporation chamber. The steam compressor can compress water vapor, increase the temperature and pressure of the water vapor, which is more conducive to the flow of water vapor and the heating of the evaporation tubes.

[0048] In a specific embodiment, the temperature range of the water vapor after passing through the steam compressor is 95 - 105 degrees Celsius.

[0049] A water vapor outlet is provided on the side wall of the outer shell of the evaporation chamber. Further, a water vapor outlet is respectively provided above and below the water vapor inlet.

[0050] After the water vapor in the evaporation chamber flows out from the water vapor outlet, a part of it passes through the heat exchanger along the pipeline, preheats the heavy oil produced water about to enter the separation chamber, and then enters the steam - water separation tank.

[0051] After the water vapor in the evaporation chamber flows out from the water vapor outlet, another part enters the distilled water tank along the pipeline to form distilled water. The distilled water in the distilled water tank flows out from the bottom of the distilled water tank along the pipeline. A part of it circulates back into the distilled water tank again to facilitate the formation of distilled water from water vapor; another part passes through the heat exchanger along the pipeline to preheat the heavy oil produced water about to enter the separation chamber.

[0052] The distilled water flowing out from the heat exchanger, a part of it enters the steam - water separation tank along the pipeline and mixes with the water vapor in the steam - water separation tank; another part is directly discharged as condensed water.

[0053] In a specific embodiment, the flow rate of the distilled water flowing through the heat exchanger is 2.5 - 3.5m 3 / h.

[0054] The heavy oil produced water treatment process provided by the present invention has many advantages compared with the existing membrane process and conventional thermal process.

[0055] Compared with the existing membrane process, the present invention has lower requirements for water quality, can treat sewage with extremely harsh water quality such as heavy oil produced water, and has lower maintenance cost compared with the existing membrane process.

[0056] Compared with the existing conventional thermal process, the present invention consumes less energy. During actual use, the overall total power of the treatment device of the present invention can be controlled within 200 kw / h. In a specific embodiment, the total power of the treatment device of the present invention is 192.4 kw / h.

[0057] In an embodiment of the present invention, a scale inhibitor is provided, including: hydroxyethylidene diphosphonic acid, aminotrimethyl phosphonic acid, PBTCA, and polyaspartic acid.

[0058] In a specific embodiment provided by the present invention, the components of the scale inhibitor are proportioned by weight. Among them, 40-50 parts of hydroxyethylidene diphosphonic acid, 10-20 parts of aminotrimethylphosphonic acid, 5-10 parts of PBTCA, and 5-10 parts of polyaspartic acid.

[0059] According to the water quality analysis results of heavy oil produced water, it is judged that the scale-forming ions are cations such as calcium, magnesium, strontium, and anions such as sulfate and carbonate. The scale inhibitor provided by the present invention can reduce the scale formation rate of heavy oil produced water in a working environment of 60-105 °C.

[0060] In this embodiment, the heavy oil produced water and the scale inhibitor are respectively added to the separation chamber through different channels, and the addition amounts of the heavy oil produced water and the scale inhibitor can be respectively adjusted. By adjusting the addition amounts of the heavy oil produced water and the scale inhibitor, the concentration of the scale inhibitor in the heavy oil produced water is adjusted.

[0061] A plurality of filling ports for adding the scale inhibitor are provided on the separation chamber. The plurality of filling ports are evenly distributed along the circumferential direction of the falling film evaporator, and the amount of the scale inhibitor is adjusted through the filling ports.

[0062] In a preferred embodiment, a flow meter for measuring the flow rate of the heavy oil produced water is provided on the separation chamber.

[0063] Furthermore, the flow meter is arranged at the water injection port of the separation chamber to reduce the influence of the internal fluid of the separation chamber on the accuracy of flow rate detection.

[0064] In a preferred embodiment, the flow meter is an ultrasonic flow meter. Using an ultrasonic flow meter can detect the flow rate more accurately. On the one hand, the amount of heavy oil produced water can be adjusted according to the processing capacity of the separation chamber, and on the other hand, the addition amount of the scale inhibitor can be adjusted according to the amount of heavy oil produced water.

[0065] In a preferred embodiment, each liter of heavy oil produced water corresponds to 6-9 mg of scale inhibitor.

[0066] The scale inhibitors in the prior art can only inhibit scale for a single substance. For example, if the scale inhibition rate for CaCO3 can reach 80%, it is difficult for the scale inhibition rate of SrSO4 to reach 60%; if the scale inhibition rate for SrSO4 can reach 80%, the scale inhibition rate of CaCO3 is difficult to exceed 50%.

[0067] It has been experimentally proven that, according to the process flow of the present invention, at a temperature of 60 - 105 °C, the scale inhibition rate is above 85%. Specifically, during the actual operation process, 4 - 5 mg of hydroxyethylidene diphosphonic acid, 1 - 2 mg of aminotrimethyl phosphonic acid, 0.5 - 1 mg of PBTCA, and 0.5 - 1 mg of polyaspartic acid are added corresponding to each liter of heavy oil produced water. After using the scale inhibitor of the present invention, the CaCO3 scale prevention rate is greater than 89.5%, and the SrSO4 scale prevention rate is greater than 87.8%.

[0068] In the description of the present invention, it should be understood that the terms "first" and "second" are only used for descriptive purposes and cannot be construed as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Thus, the features defined with "first" and "second" may explicitly or implicitly include one or more of such features. In the description of the present invention, "a plurality" means two or more unless otherwise specifically defined.

[0069] In the present invention, unless otherwise clearly defined and limited, the terms "installed", "connected", "connected to", "fixed", etc. shall be construed in a broad sense. For example, it may be a fixed connection, a detachable connection, or an integral connection; it may be a mechanical connection or an electrical connection; it may be directly connected or indirectly connected through an intermediate medium, and it may be the communication inside two components. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0070] In the description of this specification, the description with reference to terms such as "one embodiment", "some embodiments", "example", "specific example", or "some examples" means that the specific features, structures, materials, or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described can be combined in a suitable manner in any one or more embodiments or examples.

[0071] Finally, it should be noted that the above are only the preferred implementation schemes of the present invention and do not constitute any limitation to the present invention. Although the present invention has been described in detail with reference to the foregoing implementation schemes, for those skilled in the art, it is still possible to modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements for some of the technical features. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A heavy oil produced water treatment process, characterized in that, It includes the following steps: Step S1: Make the produced water of heavy oil flow in a film from top to bottom along the evaporation pipe, and heat the evaporation pipe to evaporate the water phase in the produced water of heavy oil into the first water vapor; Step S2: Collect the first water vapor and perform purification treatment on it.

2. The heavy oil produced water treatment process according to claim 1, characterized in that, In the step S1, the evaporation pipe is heated by steam heating.

3. The heavy oil produced water treatment process according to claim 1, characterized in that, The first water vapor after the purification treatment in the step S2 is used to heat the evaporation pipe.

4. The heavy oil produced water treatment process according to claim 3, characterized in that, After the first water vapor heats the evaporation pipe, part of it enters the distilled water tank to form distilled water, and the other part exchanges heat with the produced water of heavy oil.

5. The heavy oil produced water treatment process according to claim 4, characterized in that, The distilled water in the distilled water tank is used to exchange heat with the produced water of heavy oil.

6. The heavy oil produced water treatment process according to claim 5, characterized in that, The first water vapor after heat exchange and part of the distilled water are discharged into a steam-water separation tank for steam-water separation, and the other part of the distilled water is directly discharged.

7. The heavy oil produced water treatment process according to claim 1, characterized in that, In the step S1, before the produced water of heavy oil enters the evaporation pipe, oil removal treatment is performed.

8. The heavy oil produced water treatment process according to any one of claims 1 to 7, characterized in that, A separation chamber is connected below the evaporation pipe. The separation chamber is used to receive the produced water of heavy oil to be treated and the produced liquid of heavy oil after being treated by the evaporation pipe. The lower end of the separation chamber is connected to the upper part of the evaporation pipe through a circulation pump.

9. The heavy oil produced water treatment process according to claim 8, characterized in that, The produced water of heavy oil to be treated is preheated before entering the separation chamber.

10. The heavy oil produced water treatment process according to claim 9, characterized in that, An oil removal device is arranged between the lower end of the separation chamber and the upper end of the evaporation pipe, and the concentrated liquid formed after passing through the oil removal device is directly discharged.