A heavy viscous oil electric dehydrator internal water-containing crude oil steady-state pretreatment method

Abstract

The present application belongs to the technical field of oil and gas field ground engineering, and discloses a heavy and viscous oil electric dehydrator internal water-containing crude oil steady-state pretreatment method. By reducing the water content fluctuation of the inlet liquid, the water content fluctuation of the high-frequency composite electric field inlet liquid is reduced, the high-frequency composite electric field parameter stability is promoted, the stable water content condition of the inlet liquid is created for the direct current and alternating current electric field of the upper part of the electric dehydrator, the electric field parameter is stable, and stable dehydration is realized. The stability of the related electric field parameters is beneficial to further optimize the operation parameters, reduce the energy consumption, thereby reduce the operation cost, improve the overall efficiency and benefit, and is beneficial to the expansion of the application scale and range of the electric dehydrating technology in the heavy and viscous oil treatment field.

Description

Technical Field

[0001] This invention belongs to the field of oil and gas field surface engineering technology, and relates to a steady-state pretreatment method for water-containing crude oil inside an electrostatic precipitator for heavy oil. Specifically, it relates to a pretreatment method that links homogenization to reduce fluctuations in the water content of the influent and improves the stability of electric field dehydration in an electrostatic precipitator. Background Technology

[0002] Heavy oil accounts for 70% of the world's remaining oil resources, representing a significant replacement for global oil reserves. my country has a wide distribution of heavy oil resources. Dehydration of water-containing crude oil is a crucial step in crude oil production. Internationally, heavy oil dehydration generally employs a closed-loop dehydration process with added diluents. In my country, some oilfields use a closed-loop dehydration process combining thermochemical sedimentation with electrochemical dehydration, while others employ a two-stage thermochemical sedimentation dehydration process.

[0003] Currently, the major heavy oil blocks in China have all entered the middle and late stages of development. In order to improve the current situation of oilfield production, which is characterized by the expansion of development scale, increasingly complex properties of produced fluids, high processing difficulty and high cost, and in order to meet the external environmental requirements of continuously improving environmental protection standards, it is an inevitable trend to explore and study closed dehydration technology for heavy oil.

[0004] Heavy oil refers to crude oil with a viscosity of 0.916 g / cm³ at 20°C. 3 <Density ≤0.996g / cm³ 3 Furthermore, the crude oil has a viscosity >400 mPa·s at 50℃. The main technological direction for achieving closed-loop, high-efficiency oil-water separation of heavy crude oil is novel electro-dehydration technology.

[0005] In crude oil dehydration systems (such as the ultrasonic crude oil dehydration system disclosed in CN100460485C), heavy oil is difficult to dehydrate due to its high degree of emulsification, small density difference with water, and high viscosity, making it difficult to meet the crude oil dehydration qualification standards. Since the physical properties and water content fluctuations of heavy oil significantly affect the stable operation of the electrostatic dehydration unit, a steady-state pretreatment method that combines homogenization and electric field dehydration to reduce water content fluctuations in the influent during the electrostatic dehydration process helps to ensure that the heavy oil meets the standards for subsequent deep dehydration. Summary of the Invention

[0006] To overcome the shortcomings of existing technologies, this invention provides a steady-state pretreatment method for water-containing crude oil inside a heavy oil electrostatic dehydrator. By reducing the fluctuation of the water content of the influent, the fluctuation of the water content of the influent in the high-frequency composite electric field is reduced, and the high-frequency composite electric field parameters are stabilized. This creates stable influent water content conditions for the DC and AC / DC electric fields of the upper deep treatment of the electrostatic dehydrator, and stabilizes the electric field parameters, thereby achieving a stable dehydration effect.

[0007] The above-mentioned objective of this invention is achieved through the following technical solution:

[0008] A steady-state pretreatment method for water-containing crude oil inside a heavy oil electrostatic dehydrator is proposed. By reducing the fluctuation of water content in the influent, the fluctuation of water content in the influent of the high-frequency composite electric field is reduced, and the high-frequency composite electric field parameters are stabilized. This creates stable influent water content conditions for the DC and AC / DC electric fields of the upper deep treatment of the electrostatic dehydrator, and stabilizes the electric field parameters, thereby achieving stable dehydration.

[0009] The processing method of the present invention is applied in the pretreatment section of an electrostatic dehydrator.

[0010] Specifically, to reduce the fluctuation of the water content of the feed liquid, the method is to use the feed liquid to enter the upper electrode region of the oil-water interface to reduce the impact of the change in the water content of the feed liquid on the electric field.

[0011] The upper part of the electric dehydrator uses a combination electrode design with the same frequency but different voltages to cope with different water content states of the influent.

[0012] After the feed liquid is treated to reduce the fluctuation of crude oil water content, it enters the relatively low-pressure electrode plate area to treat the "water-in-oil" emulsion and assist in the treatment of large "oil-in-water" particles; then it enters the relatively high-pressure electrode plate area to treat the large "oil-in-water" particles.

[0013] After processing by the method provided by this invention, the water content of the pretreated crude oil is stabilized at 5% to 15%. The stabilized low-water-content crude oil then enters the deep processing section of an electrostatic dehydrator for further processing.

[0014] Furthermore, the upper part of the electric dehydrator uses a three-layer combined electrode plate; specifically, three electrode plates are set from top to bottom, named the first electrode plate, the second electrode plate, and the third electrode plate respectively.

[0015] The area between the first and second electrode plates is a high-voltage region. The area between the second and third electrode plates is a low-voltage region.

[0016] The electric field strength in the high-voltage region is 150-200 V / cm.

[0017] The electric field strength in the low voltage region is 100 V / cm.

[0018] Furthermore, in the steady-state pretreatment method for water-containing crude oil inside the heavy oil electrostatic dehydrator provided by the present invention, the flow of the incoming liquid in the electrostatic dehydrator is from bottom to top.

[0019] Furthermore, in the steady-state pretreatment method for water-containing crude oil inside the heavy oil electrostatic dehydrator provided by the present invention, the position of the liquid inlet pipe for liquid inlet is set in the upper electrode area of ​​the oil-water interface in the electrostatic dehydrator.

[0020] This invention also claims protection for the application of the provided steady-state pretreatment method for water-containing crude oil inside a heavy oil electrostatic dehydrator in the treatment of crude oil, wherein the crude oil is heavy oil with a density of 0.962–0.976 g / cm³ at 20°C. 3 The dehydration temperature is 89℃~92℃.

[0021] Although a buffer tank is added before the electrostatic dehydrator to stabilize the overall water content of the incoming liquid, the density difference between heavy oil with a water content of 5%–30% and water is extremely small. Therefore, when heavy oil with a water content of 5%–30% enters the lower layer of the oil-water interface, the water content of the crude oil entering the electrode zone increases, easily causing the electric field to "break down" and failing to achieve the dehydration purpose. By reducing the fluctuation of the incoming liquid water content, the fluctuation of the incoming liquid water content in the high-frequency composite electric field is reduced, promoting the stability of the high-frequency composite electric field parameters. This creates stable incoming liquid water content conditions for the DC and AC / DC electric fields in the upper part of the electrostatic dehydrator (i.e., the subsequent entry of the liquid flow), and stabilizes the electric field parameters, thereby achieving a stable dehydration effect. The stability of the relevant electric field parameters is conducive to further optimizing operating parameters, reducing energy consumption, thereby reducing operating costs, improving overall efficiency and benefits, and expanding the application scale and scope of electrostatic dehydration technology in the field of heavy oil processing.

[0022] The advantages of this invention compared to the prior art are:

[0023] This invention provides a steady-state pretreatment method for water-containing crude oil inside a heavy oil electrostatic precipitator. It solves the problem of water content fluctuations affecting the effectiveness of the electrostatic precipitator and broadens the limit on the water content entering the electrostatic precipitator (the current standard SY / T0045 requires that the water content of crude oil entering the electrostatic precipitator must be ≤30%). This can promote and facilitate the large-scale application of closed-loop electrostatic precipitator treatment of produced fluid in high water-cut areas. In terms of economic benefits, compared to the conventional design with four electrode plates, the design using three combined electrode plates increases the effective electric field space, increasing the dehydration capacity by 10%–15% compared to electrostatic precipitators of the same specifications, and the dehydration effect is more stable. Simultaneously, it saves on corresponding transformers and auxiliary facilities, reducing related equipment investment. Furthermore, it allows for smaller equipment sizes in applications requiring smaller volumes of treated fluid, and also has application potential in offshore environments where equipment size is limited. Attached Figure Description

[0024] To more clearly illustrate the technical solutions in this invention or related technologies, the accompanying drawings used in the description of the embodiments or related technologies will be briefly introduced below. Obviously, the accompanying drawings described below are some embodiments of this invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0025] Figure 1 This is a schematic diagram of the electric field arrangement of the electric dehydrator (pretreatment section) in the steady-state pretreatment method for water-containing crude oil inside the electric dehydrator of heavy oil according to the present invention. Detailed Implementation

[0026] The technical solution of the present invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0027] The present invention is described in detail below through specific embodiments, but this does not limit the scope of protection of the present invention. Unless otherwise specified, the experimental methods used in the present invention are all conventional methods, and the experimental equipment, materials, reagents, etc. used can all be obtained commercially.

[0028] In the description of this invention, it should be noted that the terms "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing the invention and for simplifying the description, and do not indicate or imply that the device or component 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 the invention. Furthermore, the terms "first," "second," and "third" are used only for distinction and should not be construed as indicating or implying relative importance.

[0029] Furthermore, the technical features involved in the different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0030] To make the objectives, technical solutions, and advantages of the present invention clearer, the embodiments of the present invention will be described in further detail below with reference to the accompanying drawings.

[0031] This invention provides a steady-state pretreatment method for water-containing crude oil inside a heavy oil electrostatic dehydrator. By reducing the fluctuation of water content in the influent, the fluctuation of water content in the influent of the high-frequency composite electric field is reduced, which promotes the stability of the high-frequency composite electric field parameters. This creates stable influent water content conditions for the DC and AC / DC electric fields of the upper deep treatment of the electrostatic dehydrator, and stabilizes the electric field parameters, thereby achieving stable dehydration.

[0032] The processing method of the present invention is applied in the pretreatment section of an electrostatic dehydrator.

[0033] Specifically, to reduce the fluctuation of the water content of the feed liquid, the method is to use the feed liquid to enter the upper electrode region of the oil-water interface to reduce the impact of the change in the water content of the feed liquid on the electric field.

[0034] The upper part of the electric dehydrator uses a combination electrode design with the same frequency but different voltages to cope with different water content states of the influent.

[0035] After the feed liquid is treated to reduce the fluctuation of crude oil water content, it enters the relatively low-pressure electrode plate area to treat the "water-in-oil" emulsion and assist in the treatment of large "oil-in-water" particles; then it enters the relatively high-pressure electrode plate area to treat the large "oil-in-water" particles.

[0036] After processing by the method provided by this invention, the water content of the pretreated crude oil is stabilized at 5% to 15%. The stabilized low-water-content crude oil then enters the deep processing section of an electrostatic dehydrator for further processing.

[0037] The upper part of the electric dehydrator uses a three-layer combined electrode plate; specifically, three electrode plates are set from top to bottom and named the first electrode plate, the second electrode plate, and the third electrode plate respectively.

[0038] The area between the first and second electrode plates is a high-voltage region. The area between the second and third electrode plates is a low-voltage region.

[0039] The electric field strength in the high-voltage region is 150-200 V / cm.

[0040] The electric field strength in the low voltage region is 100 V / cm.

[0041] In the steady-state pretreatment method for water-containing crude oil inside the electrostatic dehydrator provided by the present invention, the flow of the incoming liquid in the electrostatic dehydrator is from bottom to top.

[0042] In the steady-state pretreatment method for water-containing crude oil inside the heavy oil electrostatic dehydrator provided by the present invention, the inlet pipe is located in the upper electrode area of ​​the oil-water interface in the electrostatic dehydrator.

[0043] The crude oil is heavy oil, with a density of 0.962–0.976 g / cm³ at 20°C. 3 The dehydration temperature is 89℃~92℃.

[0044] Example 1

[0045] In electrostatic dehydrators, based on practical experience, the overall moisture content in the area from the upper layer of the oil-water interface to the lower layer of the electrode plate is generally around 50%, with a volume of 40m³. 3 The influent flow rate is 500m³. 3 Taking / d as an example, the relevant calculation explanation is as follows:

[0046] The water content of crude oil entering the high-frequency composite electric field is 30% to 40%, and the water content of crude oil exiting the high-frequency composite electric field is 10.0% to 20.0%. The water content decreases nonlinearly with height from bottom to top in this range.

[0047] Under the condition that the influent contains 2.0% water:

[0048] Overall moisture content (%) of the incoming liquid after entering the electrostatic dehydrator

[0049] =Set the volume (m) corresponding to the height of the liquid inlet 3 ) × Moisture content (%) at the corresponding height inside the electrostatic dehydrator + Volume (m³) corresponding to the oil-water interface height 3 × Incoming liquid moisture content (%) / Volume corresponding to the set inlet height (m³) 3 The volume corresponding to the oil-water interface height (m3) is 31.0%.

[0050] Under the condition that the influent contains 40.0% water:

[0051] Overall moisture content (%) of the incoming liquid after entering the electrostatic dehydrator

[0052] =Set the volume (m) corresponding to the height of the liquid inlet 3 ) × Moisture content (%) at the corresponding height inside the electrostatic dehydrator + Volume (m³) corresponding to the oil-water interface height 3 × Incoming liquid moisture content (%) / Volume corresponding to the set inlet height (m³) 3 + Oil-water interface height corresponding to volume (m³) 3 ) = 46%

[0053] Actual sampling and testing showed that the water content of crude oil entering the high-frequency composite electric field ranged from 30.0% to 50.0%, which is consistent with the above calculation results.

[0054] After the crude oil undergoes treatment to reduce fluctuations in water content, crude oil with a water content of 30%–50% enters the relatively low-pressure electrode plate area. This area primarily treats "oil-in-water" emulsions and secondarily treats large-particle "water-in-oil" emulsions. After treatment, the crude oil water content is reduced to 20%–30%. Due to the use of lower voltage, the total power consumption during demulsification and dehydration is lower, saving some energy. The crude oil then enters the relatively high-pressure electrode plate area, where it primarily treats large-particle "water-in-oil" emulsions. Through the organic combination of the three pretreatment methods of this invention, the pretreated crude oil is stabilized at 10%–20%. This stable, low-water-content crude oil then enters the deep treatment section within the electrostatic dehydrator, providing strong support for subsequent dehydration.

[0055] Example 2

[0056] A steady-state pretreatment method for water-containing crude oil inside a heavy oil electrostatic dehydrator is proposed. By reducing the fluctuation of water content in the influent, the fluctuation of water content in the influent of the high-frequency composite electric field is reduced, and the high-frequency composite electric field parameters are stabilized. This creates stable influent water content conditions for the DC and AC / DC electric fields of the upper deep treatment of the electrostatic dehydrator, and stabilizes the electric field parameters, thereby achieving stable dehydration.

[0057] The embodiments described above are merely preferred embodiments of the present invention, and not all feasible embodiments of the present invention. For those skilled in the art, any obvious modifications made without departing from the principles and spirit of the present invention should be considered to be included within the scope of protection of the claims. Although the present invention has been described above with reference to embodiments, various modifications can be made and components can be replaced with equivalents without departing from the scope of the present invention. In particular, as long as there is no technical conflict, the features in the embodiments disclosed in the present invention can be combined with each other in any way. The lack of an exhaustive description of these combinations in this specification is merely for the sake of brevity and resource conservation. Therefore, the present invention is not limited to the specific embodiments disclosed herein, but includes all technical solutions falling within the scope of the claims.

Claims

1. A steady-state pretreatment method for water-containing crude oil inside a heavy oil electrostatic dehydrator, characterized in that, By reducing the fluctuation of the influent moisture content, the fluctuation of the influent moisture content in the high-frequency composite electric field is reduced, which promotes the stability of the high-frequency composite electric field parameters. This creates stable influent moisture content conditions for the DC and AC / DC electric fields in the upper deep treatment of the electric dehydrator, and stabilizes the electric field parameters, thus achieving stable dehydration.

2. The method for steady-state pretreatment of water-containing crude oil inside a heavy oil electrostatic dehydrator as described in claim 1, characterized in that, Specifically, to reduce the fluctuation of the water content of the feed liquid, the method is to use the feed liquid to enter the upper electrode region of the oil-water interface to reduce the impact of the change in the water content of the feed liquid on the electric field.

3. The method for steady-state pretreatment of water-containing crude oil inside a heavy oil electrostatic dehydrator as described in claim 1, characterized in that, The upper part of the electric dehydrator uses a combination electrode design with the same frequency but different voltages to cope with different water content states of the influent.

4. The method for steady-state pretreatment of water-containing crude oil inside a heavy oil electrostatic dehydrator as described in claim 1, characterized in that, After the feed liquid is treated to reduce the fluctuation of crude oil water content, it enters the relatively low-pressure electrode plate area to process the "water-in-oil" emulsion and assist in the processing of large "oil-in-water" particles; then it enters the relatively high-pressure electrode plate area to process the large "oil-in-water" particles.

5. The method for steady-state pretreatment of water-containing crude oil inside a heavy oil electrostatic dehydrator as described in claim 1, characterized in that, The liquid flow in the electric dehydrator is from bottom to top.

6. The method for steady-state pretreatment of water-containing crude oil inside a heavy oil electrostatic dehydrator as described in claim 1, characterized in that, The liquid inlet pipe is positioned within the upper electrode area of ​​the oil-water interface in the electrostatic dehydrator.

7. The method for steady-state pretreatment of water-containing crude oil inside a heavy oil electrostatic dehydrator as described in claim 1, characterized in that, The upper part of the electric dehydrator uses a three-layer combined electrode plate; specifically, three electrode plates are set from top to bottom and named the first electrode plate, the second electrode plate, and the third electrode plate respectively.

8. The method for steady-state pretreatment of water-containing crude oil inside a heavy oil electrostatic dehydrator as described in claim 7, characterized in that, The area between the first and second electrode plates is a high-voltage region; the area between the second and third electrode plates is a low-voltage region.

9. The application of the pretreatment method as described in any one of claims 1-8 in the processing of crude oil.

10. The application as described in claim 9, characterized in that, The method is applied in the pretreatment section of an electrostatic dehydrator.

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