Multi-component on-line monitoring and characterization system for oilfield produced water

Abstract

The present application relates to the technical fields of fluid component detection, and discloses a kind of oilfield produced water multi-component online monitoring and characterization system, comprising: fluid flow unit, with contraction section, throat section and diffusion section, utilize flow field shear stress to realize oil droplet particle size homogenization;Polarized irradiation unit is used for projecting monochromatic linearly polarized light;Homotropic transmission detection unit and orthogonal scattering detection unit are used for collecting penetrating light intensity and orthogonal polarization scattering light intensity;Operation processing unit, according to orthogonal polarization scattering signal establishes anisotropic component compensation reference, and deducts the attenuation share generated by suspended solid from transmission signal, obtains oil phase concentration characteristic quantity, the present application utilizes the physical difference of different topography particle depolarization effect to establish component decoupling mechanism, eliminates parasitic interference of irregular suspended solid to oil phase optical response, ensures that oil phase characterization result has high stability.

Description

Technical Field

[0001] This invention relates to an online monitoring and characterization system for multiple components of produced water in oilfields, belonging to the field of fluid composition detection technology. Background Technology

[0002] In the current oilfield surface engineering produced water gathering and injection treatment process, real-time monitoring of oil concentration and suspended solids concentration is of great significance for ensuring the quality of injected water. Currently, the industry generally adopts luminescence measurement methods, using the transmission attenuation of monochromatic light after penetrating the fluid to characterize oil concentration, and using the intensity of lateral scattering signal to characterize suspended solids concentration. For multiphase fluid systems containing emulsified crude oil droplets and irregular inorganic suspended particles, existing monitoring systems usually assume that oil droplets absorb light and suspended solids scatter light. However, under real engineering conditions, micron-sized spherical emulsified oil droplets also produce Mie scattering, and irregular polyhedral solid particles block and absorb direct light, causing the optical responses of different components to overlap at the physical layer, resulting in aliasing of the signals captured by the sensor.

[0003] To mitigate signal interference, existing improvement approaches typically involve increasing the detection angle or introducing numerical fitting algorithms. However, in field environments with high salinity and fluctuating water quality background values, simply increasing the detection angle is insufficient to address physical layer interference caused by similar refractive indices. Algorithm-based fitting models face the risk of overfitting. Furthermore, due to crude oil adhesion and inorganic scaling on the optical window under continuous fluid scouring, the signal reference experiences nonlinear drift, failing to meet the stability requirements for long-term online operation. Existing signal monitoring and component characterization methods also face limitations at the underlying logic level. For example, Chinese invention patent application CN118090532A discloses a method based on... A polarization-enhanced imaging device and method for turbid oil abrasive particles is proposed. By calculating the polarization angle of background scattered light using Stokes vectors, the imaging quality of solid abrasive particles is enhanced by filtering out medium scattering. In highly turbid multiphase systems of oilfield produced water, the oil phase is not merely an imaging background but is itself a core dispersed phase that requires precise measurement. The proposed method treats medium scattering as a simple interference signal stripping, which physically loses the ability to extract the intrinsic features of oil droplets in liquid-liquid emulsion systems. Simply relying on image enhancement cannot solve the parasitic interference on the absorption coefficient of the oil phase caused by the physical depolarization component induced by irregular solids. Under complex working conditions with drastic fluctuations in composition, there is a fundamental overlap of characteristics in the quantitative characterization of the oil phase and suspended matter.

[0004] Therefore, how to utilize the anisotropic differences in the morphology of multiphase fluid components under the action of polarized light fields to construct an online characterization system that achieves hard signal isolation at the physical detection level has become the technical problem to be solved by this invention. Summary of the Invention

[0005] To address the problem of concentration identification distortion caused by deep aliasing of optical signals from oil droplets and suspended matter under complex multiphase fluid conditions, as mentioned in the background art, the technical solution of this invention is as follows: An online monitoring and characterization system for multiple components of oilfield produced water, comprising:

[0006] The fluid guiding unit has a constriction section, a throat section and a diffusion section arranged sequentially along the fluid flow direction. The throat section is equipped with an optical measurement cavity, and the cross-sectional diameter of the throat section is smaller than that of the constriction section. This is used to break up oil droplets in the extracted water passing through the optical measurement cavity into particles with a diameter in the range of 1μm to 10μm under the action of the flow field shear force.

[0007] A polarizing illumination unit is used to project monochromatic linearly polarized light with a first polarization direction into the optical measurement cavity;

[0008] The same-direction transmission detection unit is set on the opposite side of the optical axis of the polarizing irradiation unit. Its front end is equipped with a first polarization analyzer with the transmission axis parallel to the first polarization direction. It is used to collect the same-direction polarized transmitted light intensity that maintains the first polarization direction after penetrating the extracted water and convert it into a first voltage signal.

[0009] An orthogonal scattering detection unit is set on the side of the optical measurement cavity. Its front end is equipped with a second polarization analyzer with the light transmission axis perpendicular to the first polarization direction. It is used to collect the intensity of orthogonal polarized scattered light induced by irregular suspended solids in the extracted water and convert it into a second voltage signal.

[0010] The computational processing unit is connected to the co-directional transmission detection unit and the orthogonal scattering detection unit via electrical signals. The computational processing unit is used to calculate the physical depolarization component characterizing the monochromatic linearly polarized light by the irregular suspended solid based on the second voltage signal, and uses the physical depolarization component as the anisotropic component compensation reference. The computational processing unit is also used to subtract the occlusion attenuation component generated by the irregular suspended solid from the first voltage signal based on the anisotropic component compensation reference, so as to obtain the absorption characteristic quantity characterizing the oil droplet concentration.

[0011] Preferably, the fluid guiding unit further includes a laminar flow water injection mechanism, which is connected to the optical measurement cavity and is used to inject transparent sheath fluid into the inner wall of the optical measurement cavity to form a physically isolated flow layer; the flow velocity of the extracted water in the optical measurement cavity is 0.5 m / s to 2.5 m / s, and the wavelength of the monochromatic linearly polarized light is 532 nm to 850 nm.

[0012] Preferably, the polarization illumination unit includes a monochromatic laser source and a Glan Taylor prism disposed on the output optical path of the monochromatic laser source. The Glan Taylor prism is used to establish a first polarization direction, and the extinction ratio of the first polarization direction is not less than 1000:1.

[0013] Preferably, the orthogonal scattering detection unit forms a 90° spatial angle with the optical axis of the polarizing illumination unit, and the detection window of the orthogonal scattering detection unit is provided with a narrowband filter for filtering out background light noise.

[0014] Preferably, the computational processing unit is used to calculate the component feature decoupling operator using the following formula. : ,in, The amplitude of the first voltage signal. The amplitude of the second voltage signal. The extinction correlation coefficient is used to characterize the scattering properties of irregularly suspended solids.

[0015] Preferably, the computational processing unit is used to obtain the component feature decoupling operator. Then, the state of the produced water is determined according to the following steps: Step S61, real-time monitoring of component characteristics decoupling operator. The transient rate of change; step S62, when the transient rate of change exceeds the preset change threshold, it is determined that the oil phase distribution of the produced water is in an unsteady state.

[0016] Preferably, the ratio of the diameter reduction of the constricted segment to the diameter reduction of the throat segment is 0.4 to 0.7.

[0017] Preferably, both the co-directional transmission detection unit and the orthogonal scattering detection unit integrate a temperature drift compensation circuit.

[0018] Preferably, the processing unit is also connected to an early warning module, which is used to output an alarm signal when the amount of absorbed characteristic exceeds a preset concentration threshold.

[0019] Preferably, the system also includes an automatic cleaning module, which is connected to a fluid guiding unit via a control valve for periodically injecting cleaning fluid into the optical measurement cavity.

[0020] Compared with the prior art, the beneficial effects of the present invention are:

[0021] 1. In the online monitoring of multi-component oilfield produced water, a physical decoupling mechanism based on morphological anisotropy is established by utilizing the difference in depolarization effect of different morphological particles on incident ray polarized light. Since isotropic spherical emulsified oil droplets maintain the polarization state of incident light, while anisotropic irregular inorganic suspended matter induces a physical depolarization effect, the orthogonal scattering detection unit only captures depolarized photons generated by suspended matter, thus constructing a measurement benchmark that presents physical silence for oil phase concentration fluctuations. The computational processing unit performs precise subtraction of total transmission attenuation based on this independent benchmark, eliminating parasitic interference of suspended matter obstruction on oil phase measurement and eliminating characterization distortion caused by the overlap of optical characteristics of oil phase and suspended matter phase in complex produced water.

[0022] 2. The flow field shear stress generated by the variable diameter flow channel structure causes the oil-bearing micro-elements in the produced water to physically break up and tend to become uniform in size, establishing a stable basis for the optical mapping relationship within the detection system; the uniformized micron-sized emulsified oil droplets eliminate the low-frequency noise caused by random macroscopic obstruction of the light beam by large-sized particles, ensuring that the optical response characteristics of the oil phase follow the Mie scattering boundary conditions, and combined with polarization verification topology, achieves accurate extraction of the internal component characteristics of multiphase mixed fluids.

[0023] 3. The physical isolation flow layer formed at the interface between the optical field calibration cavity and the optical components in the laminar flow water injection unit blocks the direct contact between the high-salinity produced water and the surface of the optical window, maintaining the polarization neutrality of photons when passing through the interface; in conjunction with the spatial energy distribution ratio logic of co-polarized light and orthogonal polarized light, the absolute light intensity measurement is converted into a relative optical ratio calculation, which offsets the common-mode attenuation caused by the aging of the light source or the decrease in the transmittance of the optical window, ensuring the measurement stability of the system under the continuous flow conditions in the oilfield. Attached Figure Description

[0024] Figure 1 This is a block diagram illustrating the detection principle of physical decoupling of polarized light field in this invention;

[0025] Figure 2 This is a schematic diagram showing the overall functional modules and their connections in the system of the present invention.

[0026] The objectives, features, and advantages of this invention will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation

[0027] The technical solutions of the embodiments of this application will be clearly described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of this application are within the scope of protection of this application.

[0028] An online monitoring and characterization system for multiple components of produced water from oilfields includes:

[0029] The fluid guiding unit has a constriction section, a throat section and a diffusion section arranged sequentially along the fluid flow direction. The throat section is equipped with an optical measurement cavity, and the cross-sectional diameter of the throat section is smaller than that of the constriction section. This is used to break up oil droplets in the extracted water passing through the optical measurement cavity into particles with a diameter in the range of 1μm to 10μm under the action of the flow field shear force.

[0030] A polarizing illumination unit is used to project monochromatic linearly polarized light with a first polarization direction into the optical measurement cavity;

[0031] The same-direction transmission detection unit is set on the opposite side of the optical axis of the polarizing irradiation unit. Its front end is equipped with a first polarization analyzer with the transmission axis parallel to the first polarization direction. It is used to collect the same-direction polarized transmitted light intensity that maintains the first polarization direction after penetrating the extracted water and convert it into a first voltage signal.

[0032] An orthogonal scattering detection unit is set on the side of the optical measurement cavity. Its front end is equipped with a second polarization analyzer with the light transmission axis perpendicular to the first polarization direction. It is used to collect the intensity of orthogonal polarized scattered light induced by irregular suspended solids in the extracted water and convert it into a second voltage signal.

[0033] The computational processing unit is connected to the co-directional transmission detection unit and the orthogonal scattering detection unit via electrical signals. The computational processing unit is used to calculate the physical depolarization component characterizing the monochromatic linearly polarized light by the irregular suspended solid based on the second voltage signal, and uses the physical depolarization component as the anisotropic component compensation reference. The computational processing unit is also used to subtract the occlusion attenuation component generated by the irregular suspended solid from the first voltage signal based on the anisotropic component compensation reference, so as to obtain the absorption characteristic quantity characterizing the oil droplet concentration.

[0034] Preferably, the fluid guiding unit further includes a laminar flow water injection mechanism, which is connected to the optical measurement cavity and is used to inject transparent sheath fluid into the inner wall of the optical measurement cavity to form a physically isolated flow layer; the flow velocity of the extracted water in the optical measurement cavity is 0.5 m / s to 2.5 m / s, and the wavelength of the monochromatic linearly polarized light is 532 nm to 850 nm.

[0035] Preferably, the polarization illumination unit includes a monochromatic laser source and a Glan Taylor prism disposed on the output optical path of the monochromatic laser source. The Glan Taylor prism is used to establish a first polarization direction, and the extinction ratio of the first polarization direction is not less than 1000:1.

[0036] Preferably, the orthogonal scattering detection unit forms a 90° spatial angle with the optical axis of the polarizing illumination unit, and the detection window of the orthogonal scattering detection unit is provided with a narrowband filter for filtering out background light noise.

[0037] Preferably, the computational processing unit is used to calculate the component feature decoupling operator using the following formula. : in, The amplitude of the first voltage signal. The amplitude of the second voltage signal. The extinction correlation coefficient is used to characterize the scattering properties of irregularly suspended solids.

[0038] Preferably, the computational processing unit is used to obtain the component feature decoupling operator. Then, the state of the produced water is determined according to the following steps: Step S61, real-time monitoring of component characteristics decoupling operator. The transient rate of change; step S62, when the transient rate of change exceeds the preset change threshold, it is determined that the oil phase distribution of the produced water is in an unsteady state.

[0039] Preferably, the ratio of the diameter reduction of the constricted segment to the diameter reduction of the throat segment is 0.4 to 0.7.

[0040] Preferably, both the co-directional transmission detection unit and the orthogonal scattering detection unit integrate a temperature drift compensation circuit.

[0041] Preferably, the processing unit is also connected to an early warning module, which is used to output an alarm signal when the amount of absorbed characteristic exceeds a preset concentration threshold.

[0042] Preferably, the system also includes an automatic cleaning module, which is connected to a fluid guiding unit via a control valve for periodically injecting cleaning fluid into the optical measurement cavity.

[0043] Example 1: The online monitoring and characterization system for multi-component oilfield produced water provided by this invention is suitable for multiphase fluid conditions containing irregular suspended solids and emulsified oil droplets. Under a specific operating condition, the produced water contains 200 mg / L of suspended solids and 50 mg / L of emulsified crude oil. The irregularly shaped suspended solids generate non-polarization-maintaining scattering. The fluid guiding unit guides the produced water into the optical measurement cavity. The shear stress generated by the variable diameter flow channel homogenizes the oil droplet size to the range of 1 μm to 10 μm. The polarization irradiation unit projects monochromatic linearly polarized light with a first polarization direction into the optical measurement cavity. The co-polarization transmission detection unit collects the intensity of the co-polarized transmitted light that maintains the first polarization direction after penetrating the produced water through the first polarization analyzer and outputs a first voltage signal. In terms of physical principles, when monochromatic linearly polarized light irradiates emulsified oil droplets with particle sizes ranging from 1 μm to 10 μm, the depolarization ratio in the 90° orthogonal scattering direction is extremely low because this particle size range is in the Mie scattering domain and the oil droplets have high spherical isotropy. This means the scattered light from the oil droplets almost completely retains the original polarization state of the incident light. In contrast, highly irregularly shaped suspended solids cause cross-polarization scattering, making the orthogonal polarization channel (i.e., the second polarization analyzer with its transmission axis perpendicular to the first polarization direction) physically silent on the oil phase signal. Therefore, the signal captured by the orthogonal scattering detection unit can be considered as a purely physical depolarization component induced by irregular suspended solids, providing a definite physical reference for accurately removing suspended object interference from the total attenuation signal. The orthogonal scattering detection unit acquires the intensity of the orthogonally polarized scattered light induced by the irregular suspended solids through the second polarization analyzer and outputs a second voltage signal. .

[0044] The processing unit acquires the first voltage signal. With the second voltage signal According to the formula Calculate the component characteristic decoupling operator ,in, Decoupling operator for component characteristics; The amplitude of the first voltage signal; The amplitude of the second voltage signal; As the extinction correlation coefficient, the processing unit will process the second voltage signal. As a benchmark for anisotropic component compensation, the occlusion attenuation component caused by suspended solids is subtracted from the co-polarized transmission signal to obtain the characteristic quantity of oil phase concentration. Based on statistical process control, the background variability of the system is quantified, and an internally preset steady-state characteristic calibration procedure is used to determine the preset change threshold for judging the distribution state of the oil phase in the produced water. Under the initial state of connecting to a blank calibration medium without oil phase and maintaining a preset constant flow rate, the system continuously collects component characteristic decoupling operators at a fixed sampling frequency. The transient rate of change sequence of the decoupling operator within a set time window is extracted, and the arithmetic mean and standard deviation of the transient rate of change sequence are calculated. The sum of the arithmetic mean and three times the standard deviation is directly written into the register and solidified as a preset change threshold. The standard deviation characterizes the magnitude of random signal fluctuation under the physical silent state of the test platform. In the fluid component detection procedure, the transient rate of change of the main fluid operator is calculated in real time. When the absolute value of the transient rate of change exceeds the preset change threshold, the trigger pin outputs a high level, generating a hardware interrupt signal indicating the unsteady state of the produced water. The anisotropic component compensation benchmark is fed back in real time by the orthogonal scattering detection unit. This feedback loop corrects the measurement deviation caused by the fluctuation of suspended solids concentration. Based on the above physical topology, the system isolates the isotropic component at the hardware level, restores the absorption characteristics that reflect the intrinsic physical properties of oil droplets, and maintains the measurement error of oil phase concentration within 5%. The system outputs the quantified concentration value to the management terminal to provide the data basis required for process control.

[0045] Example 2: In a simulated working condition of produced water containing 200 mg / L irregular suspended solids and 50 mg / L crude oil, the test system used a circulating flow channel to verify the photoelectric response characteristics. The test platform was equipped with a linearly polarized light source with a wavelength of 650 nm and an output power set to 10 mW, with a linear polarization degree of not less than 99%. To balance the oil droplet fragmentation effect with system energy consumption, the flow velocity in the throat section was set to 2.5 m / s. The shear stress generated by this flow velocity caused the oil droplet size distribution in the optical measurement cavity to be in the range of 1 μm to 10 μm. To simulate industrial environmental interference, Gaussian white noise with a signal-to-noise ratio of 20 dB was superimposed on the original electrical signal. After the produced water flowed through the fluid guiding unit, it entered the optical measurement cavity. The first voltage signal collected by the same-direction transmission detection unit... The second voltage signal acquired by the orthogonal scattering detection unit is 342.6 mV. The signal is 45.3mV, and it contains ambient electromagnetic noise with a root mean square value of 2.1mV. The processing unit calculates the noise according to the formula... Calculate the component characteristic decoupling operator ,in, Decoupling operator for component characteristics; The amplitude of the first voltage signal; The amplitude of the second voltage signal; The extinction correlation coefficient is set to 0.85. This value was determined through pre-calibration of pure suspended solids components without an oil phase. Control group one used transmitted light intensity detection, with an output concentration characterization value of 82.4 mg / L and a measurement deviation of 64.8%. Control group two removed the fluid guiding unit, resulting in oil droplet sizes within the optical measurement cavity ranging from 10 μm to 100 μm. The measured... The values ​​fluctuate, and the error in characterizing the oil phase concentration is 18.3%.

[0046] By increasing the concentration gradient of irregularly suspended solids in the simulated medium, the detection boundary of the system was examined. When the concentration of irregularly suspended solids increased to 500 mg / L, the second voltage signal... The growth slope decreases, and the curve of the physical depolarization component changing with concentration tends to be flat. Under the condition of 200 mg / L suspended matter, the absolute error between the oil concentration measurement value output by the sample group of this invention and the physicochemical extraction analysis value is 2.4 mg / L. When photons penetrate multiphase media, the irregular morphology of suspended solids induces a change in polarization state. The system uses the orthogonal polarization component as a reference to subtract the interference component in the transmission signal and restore the intrinsic absorption component of the oil droplet. This physical decoupling mechanism based on the anisotropic difference of material morphology limits the measurement error of crude oil concentration to within 5%.

[0047] Example 3: In an online monitoring scenario of an oilfield water injection pump station with a continuous operating time of 720 hours, the light transmission window of the optical measurement cavity experiences a 12% shift in the transmission reference signal due to the formation of a non-uniform scale layer caused by mineral precipitation in the produced water. The fluid medium contains irregular suspended solids and emulsified oil droplets. The processing unit determines the extinction correlation coefficient through an initial state definition procedure. The fluid guiding unit is connected to a calibration medium containing a silt suspension but no oil phase; the polarizing irradiation unit projects monochromatic linearly polarized light with a first polarization direction into the optical measurement cavity; and the co-directional transmission detection unit and the orthogonal scattering detection unit respectively collect the first voltage signal under different silt concentration gradients. With the second voltage signal The arithmetic processing unit calculates the first voltage signal. With the second voltage signal The linear regression slope is defined as the extinction correlation coefficient. Extinction correlation coefficient To characterize the anisotropy of scattering by irregularly suspended solids, a pure water calibration medium is introduced into the system after the cleaning cycle. The processing unit calculates the window contamination compensation factor based on the ratio of the current transmitted photoelectric signal to the transmitted photoelectric signal in the initial clean state of the system. And utilize window pollution compensation factor The first voltage signal acquired in real time Amplitude correction is performed.

[0048] Flow velocity in the larynx The value is based on the dynamic viscosity of the produced water. Interfacial tension between oil and water Determined to maintain the Weber number Within the range of 10 to 12, the oil droplets passing through the optical measurement cavity are broken down under shear force to a particle size in the range of 1 μm to 10 μm; when the dynamic viscosity is... The interfacial tension is 1.2 mPa·s and the oil-water interfacial tension is... When the flow velocity is 15 mN / m, the flow velocity in the throat section Set at 3.2 m / s, based on the physical boundary law of Kelvin-Helmholtz instability at the bilayer fluid interface in fluid mechanics, the fluid guiding unit establishes a dynamic differential pressure control loop at the interface to maintain the internal physical isolation flow state boundary under a specific shear rate. The laminar water injection mechanism's pipeline input end is connected to a micro-pressure pump. The kinematic viscosity of the injected transparent sheath fluid is greater than that of the produced water base fluid. The feedback values ​​of the static pressure sensors distributed in the optical measurement cavity are read in real time to adjust the duty cycle of the micro-pressure pump drive, so that the local static pressure of the transparent sheath fluid at the injection port of the optical measurement cavity is 5 kPa to 15 kPa higher than that of the central fluid region. The differential pressure compensation parameter, combined with the fluid viscosity difference, constrains the transparent sheath fluid to adhere tightly to the surface of the optical window, forming a laminar wall-attached fluid layer with an axial flow velocity of 0.1 m / s to 0.3 m / s, forming a physical damping barrier and cutting off the radial momentum transfer from the central high Reynolds number fluid turbulence vortex to the surface of the optical window. The system utilizes the window contamination compensation factor. The signal attenuation ratio caused by window scaling is corrected, and the extinction correlation coefficient is used. From the first voltage signal The physical depolarization component caused by irregular suspended solids is subtracted to restore the absorption characteristic quantity reflecting the oil droplet concentration. Under the condition that the transmittance decreases by 12% due to window fouling, the absolute error between the oil concentration measurement value output by the processing unit and the measurement value of the laboratory infrared oil analyzer is 2.4 mg / L. The above physical parameter calibration procedure transforms the environmental interference quantity into a quantified correction operator, so that the extraction process of oil phase concentration characteristic quantity is not affected by the window fouling state and the fluctuation of irregular suspended solid concentration.

[0049] Example 4: In the scenario of initial sensor calibration for a newly commissioned gathering and transportation station, the system faces assembly residues due to the physical azimuth angle of the polarization axis inside the optical measurement cavity. The processing unit establishes an extinction reference by introducing a clean liquid with a transmittance of not less than 99.9%. The polarization illumination unit projects monochromatic linearly polarized light with a first polarization direction into the optical measurement cavity. The co-directional transmission detection unit and the orthogonal scattering detection unit respectively record the first voltage signal output by the detector. With the second voltage signal The arithmetic processing unit calculates the formula. Calculate the compensation constant ,in, As a compensation constant, The amplitude of the first voltage signal. The arithmetic processing unit will use the compensation constant to calculate the amplitude of the second voltage signal. The data is stored in a register and then used in subsequent detection processes using a compensation constant. Correct stray light signals caused by optical path tolerances to bring the anisotropic component compensation reference back to the physical zero point.

[0050] The on-site pre-deployment calibration procedure utilizes a fluid guide unit to establish a signal gain equalization relationship. By adjusting the pump flow rate, the Reynolds number of the fluid in the throat section is kept within the range of 1000 to 3000. The processing unit adjusts the photoelectric conversion coefficients of the co-directional transmission detection unit and the orthogonal scattering detection unit, ensuring that different detection channels have a consistent voltage output gradient when processing physical depolarization signals of the same intensity. After the calibration is completed, the transmission background and scattering reference inside the optical measurement cavity meet the amplitude alignment requirements, and the background interference intensity generated by hardware assembly is below 1.5%. The processing unit outputs the corrected anisotropic component compensation reference to the subsequent feature decoupling logic unit. The processing unit employs a sliding time window acquisition strategy to suppress random interference caused by fluid pulsation, specifically, acquiring the first voltage signal at a frequency of 10kHz within a time window of 100ms to 500ms. With the second voltage signal Discrete sequences are acquired, and the mean of the sequences is calculated as the effective amplitude input for that period. The setting of the time window width balances the identification efficiency of dynamic switching of medium components with the suppression effect of high-frequency electromagnetic noise, enabling the system to maintain a stable signal level gradient in an environment with drastic fluctuations in fluid Reynolds number. This time-domain processing logic converts high-frequency fluctuation characteristics into DC amplitude components that reflect the steady-state properties of the material, providing a data source for subsequent signal stripping using anisotropic component compensation reference.

[0051] Example 5: In a scenario where an inversion formula is established for produced water with an oil content gradient of 0 mg / L to 100 mg / L, the fluid guiding unit determines the boundary of the shear force field by defining geometric parameters. The contraction cone angle of the contraction section is set to 22.5°, the diffusion cone angle of the diffusion section is set to 15°, and the ratio of the axial length to the cross-sectional diameter of the throat section is set to 5. This geometric ratio ensures that the Reynolds number of the fluid passing through the optical measurement cavity is in the critical region between steady-state laminar and turbulent flow. Oil droplets physically break up under shear stress and maintain a particle size distribution of 1 μm to 10 μm. The processing unit records the component characteristics decoupling operator corresponding to samples of different concentrations. The oil phase concentration was determined based on the linear fitting results. Decoupling operator with component characteristics Function mapping between them.

[0052] The on-site deployment pre-calibration procedure utilizes a shading environment to establish the system's electronic zero-point reference. During the period when the polarization illumination unit is off, the processing unit reads the first polarization bias voltage signal from the same-direction transmission detection unit. The second polarization bias voltage signal of the orthogonal scattering detection unit And the first voltage signal collected in real time during the monitoring process With the second voltage signal The corresponding bias voltage amplitudes are subtracted to eliminate the baseline offset caused by the dark current of the photodetector. The processing unit then calculates the oil phase concentration based on the corrected voltage components. oil phase concentration The calculation formula is as follows: ;in, For oil phase concentration, and The voltage amplitude is collected in real time. and For the pre-stored bias voltage amplitude, The extinction correlation coefficient, Range proportional coefficient As the intercept constant, this adjustment eliminates the residual influence of photoelectric device temperature drift on the anisotropic component compensation reference, converting the original output at the physical signal level into a mass concentration value with stoichiometric significance; to determine the range scaling factor. With intercept constant The system implements a controlled concentration calibration procedure, selecting no fewer than five produced water samples with known oil phase concentrations, covering the entire monitoring range. Each sample is sequentially passed into the optical measurement cavity, and the corresponding component characteristics are recorded. Decoupling operator. The computational processing unit uses a decoupling operator based on measured concentration values ​​and component characteristics. The correspondence was linearly fitted using the least squares method, and the slope of the fitted curve was determined as the range scaling factor. The intercept of the fitted curve on the vertical axis is determined as the intercept constant. This procedure eliminates the influence of differences in the physical properties of crude oil components in different oilfield mining areas on the measurement results, enabling the inversion model to align with the physical properties of the fluid medium under specific operating conditions.

[0053] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the present invention can be implemented in other specific forms without departing from the spirit or essential characteristics of the present invention.

[0054] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention.

Claims

1. A multi-component online monitoring and characterization system for oilfield produced water, characterized in that, include: The fluid guiding unit has a constriction section, a throat section and a diffusion section arranged sequentially along the fluid flow direction. The throat section is equipped with an optical measurement cavity, and the cross-sectional diameter of the throat section is smaller than that of the constriction section. This is used to break up oil droplets in the extracted water passing through the optical measurement cavity into particles with a diameter in the range of 1μm to 10μm under the action of the flow field shear force. A polarizing illumination unit is used to project monochromatic linearly polarized light with a first polarization direction into the optical measurement cavity; The same-direction transmission detection unit is set on the opposite side of the optical axis of the polarizing irradiation unit. Its front end is equipped with a first polarization analyzer with the transmission axis parallel to the first polarization direction. It is used to collect the same-direction polarized transmitted light intensity that maintains the first polarization direction after penetrating the extracted water and convert it into a first voltage signal. An orthogonal scattering detection unit is set on the side of the optical measurement cavity. Its front end is equipped with a second polarization analyzer with the light transmission axis perpendicular to the first polarization direction. It is used to collect the intensity of orthogonal polarized scattered light induced by irregular suspended solids in the extracted water and convert it into a second voltage signal. The computational processing unit is connected to the co-directional transmission detection unit and the orthogonal scattering detection unit via electrical signals. The computational processing unit is used to calculate the physical depolarization component characterizing the monochromatic linearly polarized light by the irregular suspended solid based on the second voltage signal, and uses the physical depolarization component as the anisotropic component compensation reference. The computational processing unit is also used to subtract the occlusion attenuation component generated by the irregular suspended solid from the first voltage signal based on the anisotropic component compensation reference, so as to obtain the absorption characteristic quantity characterizing the oil droplet concentration.

2. The online monitoring and characterization system for multi-component oilfield produced water according to claim 1, characterized in that, The fluid guiding unit also includes a laminar flow water injection mechanism, which is connected to the optical measurement cavity and is used to inject transparent sheath fluid into the inner wall of the optical measurement cavity to form a physically isolated flow layer; the flow velocity of the extracted water in the optical measurement cavity is 0.5 m / s to 2.5 m / s, and the wavelength of the monochromatic linearly polarized light is 532 nm to 850 nm.

3. The online monitoring and characterization system for multi-component oilfield produced water according to claim 1, characterized in that, The polarization illumination unit includes a monochromatic laser source and a Glan-Taylor prism disposed on the output optical path of the monochromatic laser source. The Glan-Taylor prism is used to establish a first polarization direction, and the extinction ratio of the first polarization direction is not less than 1000:

1.

4. The online monitoring and characterization system for multi-component oilfield produced water according to claim 1, characterized in that, The orthogonal scattering detection unit forms a 90° spatial angle with the optical axis of the polarizing illumination unit, and the detection window of the orthogonal scattering detection unit is equipped with a narrowband filter for filtering out background light noise.

5. The online monitoring and characterization system for multi-component oilfield produced water according to claim 1, characterized in that, The processing unit is used to calculate the component characteristic decoupling operator using the following formula. : ,in, The amplitude of the first voltage signal. The amplitude of the second voltage signal. The extinction correlation coefficient is used to characterize the scattering properties of irregularly suspended solids.

6. The online monitoring and characterization system for multi-component oilfield produced water according to claim 5, characterized in that, The computational processing unit is used to obtain the component feature decoupling operator. Then, the state of the produced water is determined according to the following steps: Step S61, real-time monitoring of component characteristic decoupling operator. The transient rate of change; Step S62, when the transient rate of change exceeds the preset change threshold, it is determined that the oil phase distribution of the produced water is in an unsteady state.

7. The online monitoring and characterization system for multi-component oilfield produced water according to claim 1, characterized in that, The ratio of the diameter reduction of the constriction segment to that of the throat segment is 0.4 to 0.

7.

8. The online monitoring and characterization system for multi-component oilfield produced water according to claim 1, characterized in that, Both the co-directional transmission detection unit and the orthogonal scattering detection unit have integrated temperature drift compensation circuits.

9. The online monitoring and characterization system for multi-component oilfield produced water according to claim 1, characterized in that, The processing unit is also connected to an early warning module, which outputs an alarm signal when the amount of absorbed characteristic exceeds a preset concentration threshold.

10. The online monitoring and characterization system for multi-component oilfield produced water according to claim 1, characterized in that, The system also includes an automatic cleaning module, which is connected to a fluid guiding unit via a control valve to periodically inject cleaning fluid into the optical measurement cavity.

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