A spiral optical fiber-based crude oil water cut detection method and system

Abstract

The application discloses a kind of based on spiral optical fiber's crude oil water content detection method and system;The method comprises: the crude oil to be detected water content is placed in a container with super-hydrophobic super-oleophobic material is sprayed on inner wall, to realize oil-water separation up and down;Wherein, the container is coiled with a section of spiral side light emitting optical fiber from bottom to top along inner wall;The container includes but is not limited to crude oil well;After realizing oil-water separation up and down, input light wave into the side light emitting optical fiber using laser light source;Using spectrometer to detect the light wave reflected or transmitted from the side light emitting optical fiber, obtain current spectral data;Based on the current spectral data, the height of liquid level and oil-water interface in the container is determined;Based on the liquid level and the height of oil-water interface, calculate the water content of crude oil.The application can improve the detection efficiency and detection accuracy of crude oil water content, and simplify the detection process and the complexity of detection equipment.

Description

Technical Field

[0001] This invention belongs to the field of crude oil water content detection, specifically relating to a crude oil water content detection method and system based on a spiral optical fiber. Background Technology

[0002] Primary petroleum, or crude oil, extracted from the ground, typically contains water. Crude oil water content is a key indicator, significantly impacting extraction, dehydration, storage, transportation, sales, and refining processes. It also serves as important reference data in oilfield production and oil product trading.

[0003] Existing technologies for detecting crude oil water content include distillation, electrolytic desorption, hydrometer methods, X-ray methods, radio frequency methods, and capacitance methods, among others. However, these methods all require separate crude oil sample collection for testing, which is not only time-consuming and costly, but also fails to provide a comprehensive picture of the true water content of the crude oil in the well. Summary of the Invention

[0004] To address the aforementioned problems in the existing technology, this invention provides a method and system for detecting the water content of crude oil based on a spiral optical fiber.

[0005] The technical problem to be solved by this invention is achieved through the following technical solution:

[0006] A method for detecting the water content of crude oil based on a spiral optical fiber, comprising:

[0007] The crude oil with the water content to be tested is placed into a container with an inner wall coated with a superhydrophobic and superoleophobic material to achieve oil-water separation; wherein, a section of spiral-shaped side-emitting optical fiber is wound along the inner wall of the container from bottom to top; the container includes, but is not limited to, crude oil wells;

[0008] After achieving oil-water separation, a laser light source is used to input light waves into the side-emitting optical fiber;

[0009] The current spectral data is obtained by detecting the light waves reflected or transmitted from the side-emitting optical fiber using a spectrometer.

[0010] The liquid level and the height of the oil-water interface in the container are determined based on the current spectral data.

[0011] The water content of crude oil is calculated based on the liquid level height and the height of the oil-water interface.

[0012] Preferably, the calculation of crude oil water content based on the liquid level height and the height of the oil-water interface includes:

[0013] The total volume of the crude oil is determined using the liquid level height;

[0014] The volume of water in the crude oil is determined by the height of the oil-water interface, and the volume of pure petroleum in the crude oil is obtained by subtracting the volume of water from the total volume.

[0015] The water content of crude oil is calculated using the water volume, the pure oil volume, the water density, and the pure oil density.

[0016] Preferably, the method further includes the step of acquiring the ambient temperature;

[0017] The calculation of crude oil water content using the water volume, the pure petroleum volume, the water density, and the pure petroleum density includes:

[0018] The water content of crude oil is calculated using the water volume, the pure oil volume, the water density at the ambient temperature, and the pure oil density.

[0019] Preferably, the superhydrophobic and superoleophobic material includes: Teflon, nano zinc oxide, or calcium alginate.

[0020] Preferably, determining the liquid level and oil-water interface height in the container based on the current spectral data includes:

[0021] From multiple experimental spectral data obtained through pre-calibration tests, identify the target spectral data that is closest to the current spectral data;

[0022] The liquid level height and the height of the oil-water interface are determined when the target spectral data are measured, and are used as the liquid level height and the height of the oil-water interface in the container.

[0023] Preferably, the outer surface of the side-emitting optical fiber is also coated with a superhydrophobic and superoleophobic material.

[0024] Preferably, the pitch of the helical side-emitting optical fiber satisfies the following condition:

[0025] The attenuation coefficient of the side-emitting optical fiber in air is made less than a preset upper limit, and the difference between the attenuation coefficient of the side-emitting optical fiber in air and the attenuation coefficient in liquid is made greater than a preset lower limit.

[0026] The upper limit is determined based on the detection sensitivity of the spectrometer, and the lower limit is determined based on the detection accuracy of the spectrometer.

[0027] Preferably, the container further includes a sampling pool, an oil storage device, or a vertical crude oil pipeline.

[0028] This invention also provides a crude oil water content detection system based on a spiral optical fiber, comprising:

[0029] A container for holding crude oil; the inner wall of the container is coated with a superhydrophobic and superoleophobic material, and a section of spiral-shaped side-emitting optical fiber is coiled from bottom to top along the inner wall of the container; the container includes, but is not limited to, crude oil wells;

[0030] A laser source; the laser source is used to input light waves into the side-emitting optical fiber;

[0031] A spectrometer; the spectrometer is used to detect light waves reflected or transmitted from the side-emitting optical fiber to obtain current spectral data;

[0032] The data processing module is used to determine the liquid level and the height of the oil-water interface in the container based on the current spectral data, and also to calculate the water content of crude oil based on the liquid level and the height of the oil-water interface.

[0033] Preferably, the system further includes: a temperature sensor; the temperature sensor is used to detect the ambient temperature;

[0034] The data processing module calculates the water content of crude oil based on the liquid level height and the height of the oil-water interface, including:

[0035] The water content of crude oil is calculated based on the liquid level, the height of the oil-water interface, and the ambient temperature.

[0036] The crude oil water content detection method based on helical optical fiber provided by this invention involves spraying a superhydrophobic and superoleophobic material onto the inner wall of the container holding the crude oil. Utilizing the different densities and complete insolubility of pure petroleum and water, the crude oil placed in the container naturally achieves oil-water separation. A helical side-emitting optical fiber is also wound around the inner wall of the container from bottom to top. Due to the existence of the critical mode in the side-emitting optical fiber, its refractive index has different attenuation coefficients in the two different media, pure petroleum and water. Therefore, when light waves input into the side-emitting optical fiber pass through pure petroleum and water with different proportions, the light power transmitted or reflected from the side-emitting optical fiber is different. Using this characteristic, based on the spectral data of the light waves reflected or transmitted from the side-emitting optical fiber, the liquid level and the height of the oil-water interface in the container can be determined. Accordingly, knowing the liquid level and the height of the oil-water interface, the volumes of pure petroleum and water can be calculated, thereby calculating the crude oil water content. Therefore, by using the crude oil well as the aforementioned container, the overall water content of the crude oil in the well can be directly measured without sampling or analysis, resulting in rapid testing. Furthermore, compared to existing technologies that require sampling for crude oil testing, the method of measuring the overall water content of crude oil using this invention offers higher accuracy.

[0037] The present invention will now be described in further detail with reference to the accompanying drawings. Attached Figure Description

[0038] Figure 1 This is a schematic flowchart of a crude oil water content detection method based on a spiral optical fiber provided in an embodiment of the present invention;

[0039] Figure 2 yes Figure 1 A schematic diagram of the container structure in the method shown;

[0040] Figure 3 This is a schematic diagram of a crude oil water content detection system based on a spiral optical fiber provided in an embodiment of the present invention;

[0041] Figure 4 This is a schematic diagram of a crude oil water content detection system based on a spiral optical fiber provided in an embodiment of the present invention. Detailed Implementation

[0042] The present invention will be further described in detail below with reference to specific embodiments, but the implementation of the present invention is not limited thereto.

[0043] To improve the detection efficiency and accuracy of crude oil water content, and to simplify the detection process and reduce the complexity of detection equipment, this invention provides a crude oil water content detection method and system based on a spiral optical fiber.

[0044] First, a detailed description of a crude oil water content detection method based on a spiral optical fiber provided by an embodiment of the present invention will be given. In the following description, "crude oil" refers to primary petroleum containing water, while "pure petroleum" is relative to "crude oil" and refers to petroleum without water.

[0045] See Figure 1 As shown, the crude oil water content detection method based on a spiral optical fiber provided in this embodiment of the invention includes the following steps:

[0046] S10: The crude oil with the water content to be tested is placed into a container with a superhydrophobic and superoleophobic material sprayed on the inner wall to achieve oil-water separation; wherein, a spiral side-emitting optical fiber is coiled from bottom to top along the inner wall of the container.

[0047] The container may include, but is not limited to, crude oil wells. For example, it could also be a sampling pool, oil storage device, or a vertical crude oil pipeline—a regular container whose internal volume is easily calculated. When measuring the water content of crude oil in a vertical crude oil pipeline, it should be ensured that the crude oil is in a non-flowing state, and the test should be conducted only after oil and water separation.

[0048] It is understandable that water and pure petroleum have different densities and are completely incompatible. Therefore, when crude oil is placed in a container, due to the presence of superhydrophobic and superoleophobic materials, pure petroleum and water will not stick to the walls, thus achieving rapid natural separation of pure petroleum and water in the container, with pure petroleum on top and water at the bottom.

[0049] The superhydrophobic and superoleophobic materials can include Teflon, nano zinc oxide, or calcium alginate hydrogel. Specifically, Teflon can be used to form a Teflon coating on the inner wall of a container; or nano zinc oxide can be used to form numerous nano zinc oxide microspheres on the inner wall of a container; or calcium alginate can be used to form a calcium alginate hydrogel on the inner wall of a container.

[0050] Side-emitting optical fiber, also known as whole-body emitting optical fiber, not only transmits light from one end to the other but also allows light to leak from its cladding surface, making the entire fiber emit light. In this embodiment of the invention, the side-emitting optical fiber is coiled from bottom to top around the inner wall of the container, mainly to ensure that liquid at any height in the container can make light contact with the side-emitting optical fiber.

[0051] S20: After achieving oil-water separation, a laser light source is used to input light waves into the side-emitting optical fiber.

[0052] S30: Use a spectrometer to detect the light waves reflected or transmitted from the side-emitting optical fiber to obtain the current spectral data.

[0053] As is known to those skilled in the art, spectral data is curve data that can form a spectral graph. The horizontal axis of this curve represents the wavelength of light, and the vertical axis represents the power of light.

[0054] It is understandable that since liquid at any height within the container can make optical contact with the side-emitting fiber, the liquid level will affect the light waves ultimately reflected or transmitted by the fiber. In other words, the signal characteristics of the light wave ultimately output by the side-emitting fiber are generated by the combined effects of pure oil and water within the container. Furthermore, different proportions of pure oil and water in the crude oil will produce different signal characteristics, which are reflected in the intensity of the light wave ultimately output from the side-emitting fiber.

[0055] Specifically, because pure petroleum attenuates light more than water, the higher the pure petroleum content in the container, the longer the optical fiber in contact with the petroleum, resulting in greater light attenuation and consequently lower intensity of the light emitted from the side-emitting fiber. Conversely, the higher the water content in the crude oil, the longer the optical fiber in contact with the water, resulting in less light attenuation and consequently higher intensity of the light emitted from the side-emitting fiber. Therefore, the intensity of the light emitted by the side-emitting fiber differs depending on the water-to-oil ratio of the crude oil; that is, the amplitude corresponding to the vertical axis of the spectral data of the final emitted light from the side-emitting fiber varies.

[0056] S40: Determine the liquid level and oil-water interface height in the container based on the current spectral data.

[0057] Specifically, step S40 may include the following sub-steps:

[0058] (1) From the multiple experimental spectral data obtained by pre-calibration tests, find the target spectral data that is closest to the current spectral data;

[0059] (2) Determine the liquid level height and oil-water interface height corresponding to the measurement of the target spectral data, and use them as the liquid level height and oil-water interface height in the container.

[0060] There are several ways to find the target spectral data from multiple experimental spectral data in step (1). For example, in one implementation, the mean amplitude of each experimental spectral data point can be calculated, and the mean amplitude of the current spectral data point can also be calculated. Then, the experimental spectral data point with the smallest difference from the mean amplitude of the current spectral data point is taken as the target spectral data point. In another implementation, each experimental spectral data point can be subtracted from the target spectral data point to obtain a difference curve. During the subtraction, the horizontal axis corresponds one-to-one, and the amplitude corresponding to the vertical axis is subtracted. Thus, the experimental spectral data point that yields the difference curve that best fits the X-axis (a straight line with a vertical axis of 0) is taken as the target spectral data point.

[0061] In addition to considering different water-to-oil ratios during pre-calibration testing, it's also important to consider whether the density of pure petroleum contained in different batches of crude oil in the actual measurement scenario remains constant. If the density of pure petroleum contained in different batches of crude oil in the measurement scenario is not constant, then during calibration testing, experiments with various water-to-oil ratios can be conducted for pure petroleum of different densities. This way, when searching for target spectral data during actual testing, only the set of experimental spectral data corresponding to pure petroleum of the same density is used, resulting in more accurate measurement results.

[0062] S50: Calculate the water content of crude oil based on the liquid level height and the height of the oil-water interface.

[0063] Specifically, step S50 includes the following sub-steps:

[0064] (1) Use the liquid level height to determine the total volume of crude oil.

[0065] It is understandable that the shape of the container is known; for example, the shape of an oil well is cylindrical. Therefore, given the liquid level in the container, the total volume of the liquid in the container, i.e., the total volume of the crude oil, can be obtained through geometric derivation.

[0066] (2) The volume of water in crude oil is determined by the height of the oil-water interface, and the volume of pure petroleum in crude oil is obtained by subtracting the volume of water from the total volume.

[0067] Similar to step (1), given the height of the oil-water interface, the volume of water in the crude oil can be obtained through geometric derivation. Then, by subtracting the volume of water from the total volume determined in step (1), the volume of pure petroleum in the crude oil can be obtained.

[0068] (3) Calculate the water content of crude oil using the volume of water, the volume of pure petroleum, the density of water, and the density of pure petroleum.

[0069] Specifically, the water content of crude oil can be calculated using the following formula;

[0070]

[0071] Where, ρ w V represents the density of water. w ρ represents the volume of water. o V represents the density of pure petroleum. o η represents the volume of pure petroleum, and η represents the water content of crude oil.

[0072] In one implementation, if the ambient temperature of the container is not always at room temperature, the crude oil water content detection method based on spiral optical fiber provided in this embodiment of the invention can further obtain the ambient temperature, so that when calculating the crude oil water content using the above formula, the above water density and pure oil density can be converted into corresponding values ​​at the ambient temperature.

[0073] Furthermore, pure petroleum from different origins and of different qualities may have slight differences in density. Therefore, when calculating the water content of crude oil, simply substitute the corresponding density into the above formula. For example, when measuring the water content of heavy crude oil, substitute the density of heavy crude oil into the above formula.

[0074] In the crude oil water content detection method based on helical optical fiber provided in this invention embodiment, a superhydrophobic and superoleophobic material is sprayed onto the inner wall of the container holding the crude oil. Utilizing the different densities and complete insolubility of pure petroleum and water, the crude oil placed in the container naturally achieves oil-water separation. A helical side-emitting optical fiber is also wound around the inner wall of the container from bottom to top. Due to the existence of the critical mode in the side-emitting optical fiber, its refractive index has different attenuation coefficients in the two different media, pure petroleum and water. Therefore, when light waves input into the side-emitting optical fiber pass through oil and water with different ratios, the light power transmitted or reflected from the side-emitting optical fiber is different. Using this characteristic, based on the spectral data of the light waves reflected or transmitted from the side-emitting optical fiber, the liquid level and the height of the oil-water interface in the container can be determined. Accordingly, knowing the liquid level and the height of the oil-water interface, the volumes of pure petroleum and water can be calculated, thereby calculating the crude oil water content. Therefore, by using the crude oil well as the aforementioned container, the overall water content of the crude oil in the well can be directly measured without sampling or analysis, resulting in rapid testing. Furthermore, compared to existing methods that involve sampling and testing crude oil, the method for measuring the overall water content of crude oil in this embodiment of the invention offers higher accuracy.

[0075] Alternatively, in one implementation, to further improve measurement accuracy, the outer surface of the side-emitting optical fiber can also be coated with a superhydrophobic and superoleophobic material. This reduces the amount of liquid adhering to the surface of the side-emitting optical fiber, thereby reducing the impact of liquid adhesion on measurement accuracy. Of course, compared to the inner wall of an oil well, the cladding of the optical fiber is usually smooth, the amount of liquid adhering is very small, and the impact on measurement accuracy is also relatively minor.

[0076] Furthermore, the inventors discovered during the development of this invention that by adjusting the pitch of the spiral-shaped side-emitting optical fiber, the intensity and range of the light waves output by the side-emitting optical fiber can be adjusted.

[0077] Specifically, given a fixed axial radius of the helical side-emitting fiber, the attenuation coefficient α of the side-emitting fiber in air is... a The α a The attenuation coefficient α of side-emitting optical fiber in liquid l The difference α Δ Both will increase as the pitch decreases. If the designed pitch is too small, it will cause α to increase. a If the α value is too high, the power of the light wave output from the side-emitting fiber will be too low. If the spectrometer's detection sensitivity is insufficient, it will be difficult to effectively measure this light wave. Simultaneously, when α... Δ If the value is too high, the mapping relationship between the optical power output by the side-emitting fiber and the actual water-oil ratio will not be linear.

[0078] However, if the pitch is designed to be too large, it will cause αΔ When the density is too small, although the linearity is good, the difference in light power corresponding to different water-oil ratios is not significant. If the detection accuracy of the spectrometer is low, the spectrometer will not be able to effectively distinguish this difference.

[0079] The detection sensitivity of a spectrometer can be understood as its ability to detect small signals, while the detection accuracy of a spectrometer can be understood as its ability to distinguish between similar but different signals.

[0080] Therefore, considering the above factors, when the detection sensitivity and accuracy of the spectrometer are not high enough, the pitch of the helical side-emitting optical fiber should meet the following conditions:

[0081] The attenuation coefficient α of the side-emitting fiber in air a Less than the preset upper limit, and the attenuation coefficient α of the side-emitting fiber in air. a With the attenuation coefficient α in the liquid l The difference α Δ It is greater than the preset lower limit; wherein the upper limit is determined based on the detection sensitivity of the spectrometer; and the lower limit is determined based on the detection accuracy of the spectrometer.

[0082] Specifically, the implementation method for determining the upper limit based on the detection sensitivity of the spectrometer includes: ensuring that the magnitude of the light wave containing useful information (crude oil water content information) output by the side-emitting fiber is at least greater than the minimum signal that the spectrometer can detect.

[0083] The specific implementation method for determining the lower limit based on the detection accuracy of the spectrometer includes: ensuring that, at the required crude oil water content detection accuracy (e.g., 0.1%, 1%, or 5%), the side-emitting fiber outputs different amplitudes of light waves for crude oils with adjacent water contents, and that this difference can be identified and distinguished by the spectrometer. For example, assuming the required crude oil water content detection accuracy is 1%, and assuming the amplitude of the light wave output by the side-emitting fiber for crude oil with a water content of 1% is A, for crude oil with a water content of 2% is B, and for crude oil with a water content of 3% is C; further assuming the spectrometer can only distinguish light waves with an amplitude difference of at least 5, then the designed side-emitting fiber should ensure that both BA and CB are greater than 5.

[0084] In practical applications, a mechanical stepping platform and a heater can be used to fabricate helical side-emitting optical fibers. The mechanical stepping platform includes a rotating platform and a translation stage; the translation stage is used to move the optical fiber parallel to each other, thereby causing segmented contact with the heater and generating thermal deformation; the rotating platform is used to rotate the optical fiber, thereby fabricating a regular helical shape. Specific optical fiber processing methods are not the inventive point of this invention and will not be described further.

[0085] Based on the same inventive concept, this invention also provides a crude oil water content detection system based on a spiral optical fiber, see [link to relevant documentation]. Figure 3 and Figure 4 As shown, the system includes: a container for holding crude oil, a laser light source, a spectrometer, and a data processing module.

[0086] The container has an inner wall coated with a superhydrophobic and superoleophobic material, and a spiral side-emitting optical fiber is coiled along the inner wall from bottom to top; the container includes, but is not limited to, crude oil wells.

[0087] Laser light sources are used to input light waves into side-emitting optical fibers.

[0088] Specifically, such as Figure 3 As shown, the laser source can directly input light waves into one end of the side-emitting optical fiber. Alternatively, the laser source can also be as follows: Figure 4 The light wave is input into the side-emitting optical fiber through an optical circulator, as shown.

[0089] A spectrometer is used to detect light waves reflected or transmitted from a side-emitting optical fiber to obtain current spectral data.

[0090] Specifically, if the laser source uses Figure 3 By inputting light waves into the side-emitting optical fiber as shown, the spectrometer can then... Figure 3 The light wave transmitted through the fiber is received and detected from the other end of the side-emitting fiber. However, if the laser source uses... Figure 4 By inputting light waves into the side-emitting optical fiber as shown, the spectrometer can then... Figure 4 The diagram shows the reception and detection of light waves reflected from the optical fiber from the feedback port of the optical circulator.

[0091] The data processing module is used to determine the liquid level and the height of the oil-water interface in the container based on the current spectral data, and also to calculate the water content of crude oil based on the liquid level and the height of the oil-water interface.

[0092] The method by which the data processing module determines the liquid level height and the height of the oil-water interface can be found in step S40 of the above method embodiment; the method by which the data processing module calculates the crude oil water content can be found in step S50 of the above method embodiment.

[0093] In practical applications, the data processing module can be a computer or other circuit modules integrated with a processor. This processor can be a general-purpose processor, including a Central Processing Unit (CPU), a Network Processor (NP), etc.; it can also be a Digital Signal Processor (DSP), an Application Specific Integrated Circuit (ASIC), a Field-Programmable Gate Array (FPGA), or other programmable logic devices, discrete gate or transistor logic devices, or discrete hardware components.

[0094] Optionally, the crude oil water content detection system provided in this embodiment of the invention may further include: a temperature sensor; the temperature sensor is connected to the data processing module and is used to detect the ambient temperature.

[0095] Correspondingly, the data processing module can calculate the water content of crude oil based on the liquid level, the height of the oil-water interface, and the ambient temperature.

[0096] Specifically, when the data processing module calculates the water content of crude oil in the manner described in step S50 above, it can first determine the water density and pure petroleum density at the ambient temperature, and then substitute these two parameters into the calculation formula for calculation.

[0097] It should be noted that, for the system embodiment, since it is basically similar to the method embodiment, the description is relatively simple. For relevant parts, please refer to the description of the system embodiment. The embodiments of the present invention will not be described in detail again.

[0098] In the description of this specification, "a plurality of" means two or more, unless otherwise expressly specified. The use of terms such as "an embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicates that a specific feature or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features or characteristics described may be combined in any suitable manner in one or more embodiments or examples. In addition, those skilled in the art can combine and integrate the different embodiments or examples described in this specification.

[0099] Although this application has been described herein in conjunction with various embodiments, other variations of the disclosed embodiments can be understood and implemented by those skilled in the art in carrying out the claimed application by reviewing the accompanying drawings, the disclosure, and the appended claims.

[0100] The above description, in conjunction with specific preferred embodiments, provides a further detailed explanation of the present invention. It should not be construed that the specific implementation of the present invention is limited to these descriptions. For those skilled in the art, various simple deductions or substitutions can be made without departing from the concept of the present invention, and all such modifications and substitutions should be considered within the scope of protection of the present invention.

Claims

1. A method for detecting the water content of crude oil based on a spiral optical fiber, characterized in that, include: The crude oil with the water content to be tested is placed into a container with a superhydrophobic and superoleophobic material sprayed on the inner wall to achieve oil-water separation; wherein, a section of spiral side-emitting optical fiber is coiled from bottom to top along the inner wall of the container, so that the liquid at any height in the container can make light contact with the side-emitting optical fiber; the container includes a crude oil well. After achieving oil-water separation, a laser light source is used to input light waves into the side-emitting optical fiber; The light waves reflected or transmitted from the side-emitting optical fiber are detected using a spectrometer to obtain the current spectral data; the spectral data is curve data that can form a spectral graph. The liquid level and the height of the oil-water interface in the container are determined based on the current spectral data. The crude oil water content is calculated based on the liquid level height and the height of the oil-water interface. The step of determining the liquid level and oil-water interface height in the container based on the current spectral data includes: From multiple experimental spectral data obtained through pre-calibration tests, find the target spectral data that is closest to the current spectral data. This includes: subtracting the current spectral data from each experimental spectral data, and taking the experimental spectral data that yields a difference curve that best matches the straight line with a vertical axis of 0 as the target spectral data. The liquid level height and the oil-water interface height set when the target spectral data is measured are determined as the liquid level height and the oil-water interface height in the container. The pitch of the spiral-shaped side-emitting optical fiber satisfies the following condition: The attenuation coefficient of the side-emitting optical fiber in air is made less than a preset upper limit, and the difference between the attenuation coefficient of the side-emitting optical fiber in air and the attenuation coefficient in liquid is made greater than a preset lower limit. The upper limit is determined based on the detection sensitivity of the spectrometer, and the lower limit is determined based on the detection accuracy of the spectrometer.

2. The method for detecting the water content of crude oil according to claim 1, characterized in that, The calculation of crude oil water content based on the liquid level height and the height of the oil-water interface includes: The total volume of the crude oil is determined using the liquid level height; The volume of water in the crude oil is determined by the height of the oil-water interface, and the volume of pure petroleum in the crude oil is obtained by subtracting the volume of water from the total volume. The water content of crude oil is calculated using the water volume, the pure oil volume, the water density, and the pure oil density.

3. The crude oil water content detection method according to claim 2, characterized in that, It also includes the step of obtaining the ambient temperature; The calculation of crude oil water content using the water volume, the pure petroleum volume, the water density, and the pure petroleum density includes: The water content of crude oil is calculated using the water volume, the pure oil volume, the water density at the ambient temperature, and the pure oil density.

4. The method for detecting the water content of crude oil according to claim 1, characterized in that, The superhydrophobic and superoleophobic materials include: Teflon, nano zinc oxide, or calcium alginate.

5. The method for detecting the water content of crude oil according to claim 1, characterized in that, The outer surface of the side-emitting optical fiber is also coated with a superhydrophobic and superoleophobic material.

6. The method for detecting the water content of crude oil according to claim 1, characterized in that, The container also includes: a sampling pool, an oil storage device, or a vertical crude oil pipeline.

7. A crude oil water content detection system based on a spiral optical fiber, characterized in that, include: A container for holding crude oil; the inner wall of the container is coated with a superhydrophobic and superoleophobic material, and a section of spiral-shaped side-emitting optical fiber is coiled along the inner wall of the container from bottom to top, so that liquid at any height in the container can make light contact with the side-emitting optical fiber; the container includes a crude oil well. A laser source; the laser source is used to input light waves into the side-emitting optical fiber; A spectrometer; the spectrometer is used to detect light waves reflected or transmitted from the side-emitting optical fiber to obtain current spectral data; the spectral data is curve data capable of forming a spectral graph; A data processing module; the data processing module is used to determine the liquid level height and the oil-water interface height in the container based on the current spectral data, and is also used to calculate the crude oil water content based on the liquid level height and the oil-water interface height; wherein, determining the liquid level height and the oil-water interface height in the container based on the current spectral data includes: finding a target spectral data that is closest to the current spectral data from multiple experimental spectral data obtained by pre-calibration tests, including: subtracting the current spectral data from each experimental spectral data, and taking the experimental spectral data that can be subtracted to obtain a difference curve that best fits the straight line with a vertical axis of 0 as the target spectral data.

8. The crude oil water content detection system according to claim 7, characterized in that, Also includes: Temperature sensor; the temperature sensor is used to detect ambient temperature; The data processing module calculates the water content of crude oil based on the liquid level height and the height of the oil-water interface, including: The water content of crude oil is calculated based on the liquid level height, the height of the oil-water interface, and the ambient temperature.

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