Nanobubble water concentration and nanobubble particle size detection method based on light scattering

Abstract

The invention relates to the technical field of oil and gas field development, and specifically discloses a method for detecting the concentration and particle size of nanobubble water based on light scattering. An experiment of preparing nanobubble water on the ground is carried out to measure the gas volume, water volume and generated nanobubble water volume used in preparing the nanobubble water. Lasers of different angles and wavelengths are sequentially introduced into the prepared nanobubble water, and an image of a light path and the number of photons respectively generated in the nanobubble water are captured by a light intensity detector, and the number of photons is converted into a numerical value for reading scattered light intensity. The diameter of nanobubbles in the nanobubble water is assumed, and the diameter of the nanobubbles is adjusted by a least squares algorithm until the error between theoretical scattered light intensity and the obtained scattered light intensity meets a set error. The dimensionless size parameter is calculated by using the adjusted nanobubble diameter, and a relationship between the scattered light intensity, the concentration of nanobubble water and the nanobubble radius used for detection is constructed based on Mie scattering and Rayleigh scattering.

Description

Technical Field

[0001] The invention relates to the technical field of oil and gas field development, and in particular to a method for detecting nanobubble water concentration and nanobubble particle size based on light scattering. Background Art

[0002] Nanobubble water has been used in some oil fields. As an emerging displacement method, nanobubble water has the effects of pressurization, plugging, and emulsification stripping of crude oil. Especially in low-permeability reservoirs, it can increase formation energy and increase recovery by about 10%. However, in physical simulations, it was found that the improvement of oil displacement effect by nanobubble water at different times was different. This is mainly because after the nanobubble water is prepared, it is sent to the detection agency to detect the particle size and concentration, and then the physical simulation begins. During this period, the concentration of nanobubble water will decay with the increase of time, and the size range of nanobubbles varies widely, distributed in the range of 10~600nm. The current single light scattering method causes a large error in the measurement results, resulting in a deviation between the measured particle size distribution and the true value.

[0003] Based on the current measurement methods, the main methods for measuring colloid particle size and concentration include extinction method, angle scattering method, diffraction method and screening method, sedimentation method, microscopy method, light scattering method, ultrasonic method, etc. The above methods can basically meet the measurement of existing colloid particle size and concentration, but the response to bubbles with a large particle size span may be attenuated, especially when the particle size distribution is wide, it is difficult to accurately distinguish the distribution of each particle size, resulting in the measurement result being too large or too small; at the same time, some measuring instruments have high energy consumption, high cost, and time-consuming and labor-intensive to measure colloid parameters.

[0004] Therefore, existing nanobubble water lacks more accurate and comprehensive measurement methods and means for bubble concentration and particle size information when detecting the size of bubbles with multi-particle size distribution. Summary of the invention

[0005] The purpose of the present invention is to provide a method for detecting the concentration and particle size of nanobubble water based on light scattering, so as to solve the technical problem in the prior art that the existing nanobubble water lacks a more accurate and comprehensive method and means for measuring the bubble concentration and particle size information when detecting the size of bubbles with multiple particle size distributions.

[0006] In order to solve the above technical problems, the present invention specifically provides the following technical solutions:

[0007] The method for detecting the concentration and particle size of nanobubble water based on light scattering is as follows:

[0008] Step 100, conducting an experiment of preparing nano bubble water on the ground, measuring the amount of gas and water used to prepare the nano bubble water and the amount of nano bubble water generated;

[0009] Step 200, sequentially introducing lasers of different angles and wavelengths into the prepared nanobubble water, and using a light intensity detector to capture images of the light path and the number of photons generated in the nanobubble water, and converting the number of photons into a numerical value that can be used to read the scattered light intensity;

[0010] Step 300, setting the diameter of the nanobubble in the nanobubble water, and adjusting the set diameter of the nanobubble based on a least squares algorithm until the error between the theoretical scattered light intensity and the obtained scattered light intensity meets the set error;

[0011] Step 400: Calculate the dimensionless size parameter using the adjusted nanobubble diameter , and based on Mie scattering and Rayleigh scattering, a relationship between the scattered light intensity, nanobubble water concentration and nanobubble radius was constructed;

[0012] in:

[0013] Dimensionless size parameters , the relationship based on Mie scattering is: ; ; Dimensionless size parameters , the relationship based on Rayleigh scattering is: ; ; Wherein, d is the adjusted nanobubble diameter; is the incident laser wavelength; is the radius of the nanobubble, in nanometers, Indicates the intensity of astigmatism; Indicates the concentration of nanobubble water; The volume of gas used to prepare nanobubble water on the ground, in milliliters; The amount of nanobubble water prepared for the ground, in milliliters; is a fixed value; Represents the light coefficient.

[0014] As a preferred solution of the present invention, the error calculation formula between the theoretical scattered light intensity and the obtained scattered light intensity is set to: ;

[0015] in, To calculate the error parameter; is the scattered light intensity measured in the experiment; is the theoretically calculated scattered light intensity; is the scattering angle; set the threshold value that makes the calculation error parameter converge, and use the least squares algorithm to calculate, and the calculation formula is: ;in, For the point As a preferred embodiment of the present invention, in the process of constructing a relationship between the scattered light intensity, nanobubble water concentration and nanobubble diameter for detection based on light scattering, a verification formula for the nanobubble radius and nanobubble concentration is constructed, specifically: ;

[0016] In the process of constructing the relationship between the scattered light intensity, nanobubble water concentration and nanobubble diameter for detection based on Rayleigh scattering, a verification formula for the scattered light intensity, nanobubble water concentration and nanobubble radius is constructed, specifically: ;

[0017] in, and represent the refractive index of the scatterer and the medium respectively; is the radius of the nanobubble; is the bubble concentration.

[0018] As a preferred embodiment of the present invention, in the dimensionless size parameter In the relationship based on Rayleigh scattering:

[0019] By obtaining the scattered light intensity of lasers at different wavelengths, a set of equations for solving the radius of nanobubbles is established. The ratio of the scattered light intensity between any two adjacent different wavelengths is calculated as follows: ；

[0020] in, and They represent the wavelengths of two adjacent lasers that have been arranged. and Indicates the corresponding scattered light intensity.

[0021] Furthermore, different algorithms are used to remove image noise from the acquired beam path image using median filtering and detect the beam boundary using the Canny edge detection operator, and to extract the light path profile; at the same time, the beam image of the acquired beam path image is normalized, and the value of the scattered light intensity of the image is read;

[0022] Reverse detection verification was performed by constructing a relationship between the scattered light intensity, nanobubble water concentration and nanobubble radius for detection based on Mie scattering and Rayleigh scattering.

[0023] As a preferred solution of the present invention, in step 200, the scattered light intensity at multiple angles and the converted digital signal value are measured, and the specific calculation formula is: ;

[0024] in, is an integer digital signal value; The maximum input light intensity of ADC for digital-to-analog conversion; As a preferred solution of the present invention, in step 300, the nanobubble water concentration and the nanobubble radius are processed using an unconstrained algorithm, and the specific calculation formula is: ;

[0025] in, is the adjusted nanobubble diameter, is the extinction coefficient, is the scattered light intensity; is the rated light intensity of the incident laser, is the distance from the bubble to a point on the scattering surface.

[0026] Compared with the prior art, the present invention has the following beneficial effects:

[0027] The present invention obtains parameter values ​​of gas and liquid according to the prepared nanobubble water, establishes the relationship between scattered light intensity and nanobubble concentration and particle size respectively, selects particle size distribution intervals of respective applicable ranges within the applicable wavelength range, and finally obtains a relationship model between nanobubble particle size and concentration, realizes accurate fitting of nanobubble particle size, and thus obtains more accurate and complete results. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] In order to more clearly illustrate the implementation methods of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for the implementation methods or the description of the prior art. Obviously, the drawings in the following description are only exemplary, and for ordinary technicians in this field, other implementation drawings can be derived from the provided drawings without creative work.

[0029] Figure 1 is a spatial schematic diagram of light scattering;

[0030] Figure 2 This is the light path diagram when irradiating nanobubbles;

[0031] Figure 3 Test the true values ​​for nanobubble concentration and particle size;

[0032] Figure 4 is a graph of nanobubble concentration and particle size obtained using rayleigh scattering;

[0033] Figure 5 is a graph of nanobubble concentration and particle size obtained using Mie scattering;

[0034] Figure 6 The graph of nanobubble concentration and particle size obtained by combining rayleigh and Mie scattering;

[0035] Figure 7 The nanobubble concentration and particle size curve obtained by combining rayleigh and Mie scattering at low concentration;

[0036] Figure 8 This is a comparison chart of rayleigh and the true value;

[0037] Fig. 9 The graph of nanobubble concentration and particle size obtained by comparing Mie scattering with the true value;

[0038] Fig.10 The nanobubble concentration and particle size curves obtained by combining rayleigh and Mie scattering with the true value;

[0039] Fig.11 The nanobubble concentration and particle size curves obtained by combining Rayleigh and Mie scattering with the true value at low concentration;

[0040] Fig.12 The figure is a flow chart of the method for detecting the concentration and particle size of nanobubble water based on the law of light scattering. DETAILED DESCRIPTION

[0041] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0042] like Figures 1 to 12 As shown, the present invention provides a method for detecting nanobubble water concentration and nanobubble particle size based on light scattering, comprising:

[0043] When preparing nanobubble water, a light intensity detector CMOS is used to capture the number of scattered photons, and readable scattered light intensity numerical data is obtained through analog-to-digital signal conversion, while an image of the light beam path formed by the nanobubble is obtained;

[0044] Analyze the intensity and distribution of the nanobubble beam in the beam path image, integrate the spatial distribution of the scattered light intensity according to the Lambert-Beer law, and calculate the bubble concentration;

[0045] The function-constrained algorithm and the unconstrained algorithm are used to estimate the nanobubble size parameters according to the set wavelength and scattered beam path image, and the nanobubble radius is inversely calculated.

[0046] The scattering cross section is calculated using a light scattering algorithm, and the actual size of the bubble is inferred from the scattering beam diameter in the scattering beam path image;

[0047] A model of light intensity, nanobubble water concentration and bubble radius in a light beam path image of nanobubbles based on the correspondence between nanobubble water concentration and bubble radius according to the law of light scattering is constructed.

[0048] Specifically, the Lamber-Beer law and the function constraint and unconstrained algorithm are used to process the concentration and particle size, and the calculation formula is: (1); where k is the total extinction cross section of all bubbles in a unit volume, which can be written as: (2); where C is the number density of bubbles per unit volume, in pieces / mL; D is the diameter, in nm; and m is the refractive index; is the extinction coefficient. Combining the above formulas, we can get: (3). When the diameter D of the bubble to be measured and the extinction coefficient When the attenuation of the incident light by the bubble is known, the bubble number density C can be calculated as: (4). Before preparing nanobubble water, measure the amount of gas and liquid used to prepare nanobubble water on the ground and the amount of final nanobubbles generated, specifically:

[0049] The scattered light intensity distribution function is: Complex amplitude coefficient, also known as light coefficient: in, are Bessel functions and Hankel functions of the first kind; is the Legendre function; is the size parameter, where d is the bubble size, is the wavelength of incident light. If this dimensionless parameter is less than 1, the approximate solution of light scattering theory is Rayleigh scattering. is the relative refractive index, and the expression is: ,in and represent the refractive index of the scatterer and the medium respectively; is the associated Legendre function of order 1 and degree n;

[0050] The following will calculate :

[0051] The integral expression of Bessel function is: Bessel functions and Hankel functions have the following recurrence relationship: The recursive formula can be obtained by substituting it into equations (11) and (12) and then deriving it:

[0052] For the second kind of Bessel function, substitute n=0, 1 into the calculation to get the initial value condition: Will be obtained and Substituting into (7) and (8) we can calculate , so: in, is the scattering cross section, , is the wave number of light

[0053] The following will be Calculation: in: for function, is the scattering angle, and their recursive relationship is:

[0054]

[0055] The initial value formula is: The calculated and Substituting into formula (1) and (2), we can obtain .

[0056] For the scattered light intensity perpendicular to the scattering surface The scattered light intensity parallel to the scattering surface And the total scattered light intensity There are the following expressions: When the scattered light is partially polarized, we have: Through equations (31) and (32), the total light intensity in this case is obtained as: In particular, when the size parameter When it is much smaller than 1, the formula can be written as: in is the polarizability. For nano-sized bubbles, for: Substituting into the above formula (37), we can get: Simplified to: Assuming that the concentration of nanobubble colloidal solution is C, the total scattered light intensity is equal to the bubble number density C and the scattering cross section of a single colloid The product of, that is: Substitute the above : Therefore, the above formula is simplified to the relationship between light intensity, concentration and particle size; in, .

[0057] The optical path obtained by laser irradiation is used to analyze the scattered light signal through the sensor. The concentration and particle size are processed based on the Lamber-Beer law and function constraints and unconstrained algorithms. The least squares method and numerical algorithm are used for estimation and verification to obtain the final measurement results, which are compared with the actual measured concentration and particle size of the nanobubble colloid solution, and then the results are improved to increase precision and accuracy.

[0058] Assuming that the particle size of the nanobubble is 200 nm, Mieplot is used to calculate the theoretical scattered light intensity, and the difference between theory and practice is handled by the least squares method; the value of the bubble particle size is estimated based on the iterative method to make it close to the true value.

[0059] When light shines on nanobubbles, the bubbles will scatter the light. The light intensity detector CMOS will capture the number of scattered photons and convert the light signal into an electrical signal. The strength of the electrical signal is proportional to the number of detected photons. The electrical signal strength is read by an analog-to-digital converter and processed into a digital signal. The converted data is sent to a computer, which then converts the digital signal into a readable numerical value.

[0060] When preparing nano bubble water, a laser or monochromatic light source is used to measure the scattered light intensity, the wavelength range of the light is 100-600nm, a photodiode is used as the light intensity detector CMOS, and a lens or optical fiber is used to introduce the scattered light into the light intensity detector CMOS.

[0061] The acquired beam path image is subjected to median filtering to remove image noise, the beam boundary is detected using the Canny edge detection operator, and the light path profile is extracted; meanwhile, the beam image of the acquired beam path image is normalized.

[0062] Take pictures and pre-process the pictures containing the Tyndall effect to improve the analysis accuracy. The processing methods include denoising and grayscale. Denoising generally uses median filtering to remove image noise, uses Canny edge detection to detect the beam boundary, and extracts the light path contour. Grayscale generally establishes a grayscale image normalization model (such as the Luminosity method) to normalize the collected light beam.

[0063] The reading process for CMOS image data is as follows:

[0064] ①Send a reset command to initialize the camera. Supply 5V power to the camera for power-on reset, and set the image size and compression rate to clear the cached images;

[0065] ②Send the operation instruction and start taking pictures;

[0066] ③ The size of the picture after taking the photo is the size of the space occupied. After taking the photo, read the picture in the cache area. You can set it to read it once or read it multiple times;

[0067] ④ Read the picture. When the picture is read successfully, the camera can be turned off to prevent the chip from heating up due to long-term power supply, thereby shortening the service life of the image sensor.

[0068] Obtain the scattered light intensity value, and finally convert the scattered light intensity signal into an electrical signal. The formula can be written as: ;

[0069] Where D is the digital signal value, which is an integer; I max is the maximum light intensity input to the ADC; n is the number of bits of the ADC, 12 bits. As shown in Table 1 below.

[0070] When the particle size of the nanobubbles is preset to range from 0 to 800 nm, the wavelength is 650 nm, and the refractive index of the nanobubbles in water is 1.0003, the scattered light intensity at multiple angles and the converted digital signal values ​​are measured, as shown in Table 2 below.

[0071] The specific method of constructing a model of light intensity, nanobubble water concentration and bubble radius in a light beam path image of nanobubbles based on the corresponding relationship between nanobubble water concentration and bubble radius according to the light scattering law includes:

[0072] Based on dimensionless parameters Constructed for the nanobubble size parameters:

[0073] when The relationship between scattered light intensity, nanobubble radius and concentration based on Mie scattering law;

[0074] when Relationship between scattered light intensity, nanobubble radius and concentration based on Rayleigh scattering law

[0075] in, is the diameter of the nanobubble, is the wavelength, and N is the set nanobubble radius, which is specifically 100 nm.

[0076] Dimensionless size parameters for constructing nanobubbles , , where d is the bubble size, is the incident laser wavelength; constructing a relationship between scattered light intensity, nanobubble water concentration and nanobubble radius, the relationship is: ;

[0077] set up:

[0078] The dimensionless size parameter , the relationship based on Mie scattering is: The dimensionless size parameter , the relationship based on Rayleigh scattering is: in, is the radius of the nanobubble, in nanometers, Indicates the total astigmatism intensity; represents the nanobubble concentration; The volume of gas used to prepare nanobubble water on the ground, in milliliters; The total amount of gas and liquid used to prepare nanobubbles on the ground, in milliliters; is a fixed value; Represents the light coefficient.

[0079] By measuring the scattered light intensity at different wavelengths, it is recorded as ...Establish a set of equations for light intensity and particle size, take the ratio of scattered light between two particles, and the calculation formula is as follows: The radius of the nanobubbles was calculated by fitting.

[0080] The relationship between nanobubble water concentration and particle size was calculated, and the following features were found in the image:

[0081] When Rayleigh scattering is used alone to calculate the concentration and particle size of nanobubbles, the effect fits the true value well between 0 and 100 nm. When the value is greater than 100 nm, the measured results are too small.

[0082] When Mie scattering is used alone to calculate the concentration and size of nanobubbles, the plotted values ​​are high between 0 and 100 nm, and the fit is better when it is greater than 100 nm;

[0083] The error value of the curve obtained by combining the two methods is the smallest. This method mainly selects the interval with better fitting of the first half of Rayleigh scattering and the second half of Mie scattering and redraws it.

[0084] When the concentration of bubble water becomes lower, the intensity of light scattered by the bubbles becomes weaker. When the image is processed, the light intensity signal obtained is small, and the final curve is biased downward as a whole, but the particle size is less affected.

[0085] The traditional method for colloid detection is to classify the particle size of a certain colloid into one type for solution (Rayleigh scattering or Mie scattering), and then obtain the relationship between the scattered light intensity and the concentration and particle size. However, this method ignores the problem of large bubble span, and because nanobubbles are tiny bubbles generally distributed in the range of 10~1000nm, if a single measurement method is continued to be used, accurate measurement results will not be obtained.

[0086] The invention adopts the theory of Rayleigh scattering in a small particle size range and Mie scattering in a large particle size range to establish a relationship between the scattered light intensity of nanobubbles and their particle size and concentration, thereby achieving accurate fitting of the nanobubble particle size and obtaining more accurate and complete results.

[0087] The above embodiments are only exemplary embodiments of the present application and are not intended to limit the present application. The protection scope of the present application is defined by the claims. Those skilled in the art may make various modifications or equivalent substitutions to the present application within the essence and protection scope of the present application, and such modifications or equivalent substitutions shall also be deemed to fall within the protection scope of the present application.

Claims

1. A method for detecting nanobubble water concentration and nanobubble particle size based on light scattering, characterized in that: The following methods are included: Step 100, conducting an experiment of preparing nano bubble water on the ground, measuring the amount of gas and water used to prepare the nano bubble water and the amount of nano bubble water generated; Step 200, sequentially introducing lasers of different angles and wavelengths into the prepared nanobubble water, and using a light intensity detector to capture images of the light path and the number of photons generated in the nanobubble water, and converting the number of photons into a numerical value that can be used to read the scattered light intensity; Step 300, setting the diameter of the nanobubble in the nanobubble water, and adjusting the set diameter of the nanobubble based on a least squares algorithm until the error between the theoretical scattered light intensity and the obtained scattered light intensity meets the set error; Wherein, by analyzing the intensity and distribution of the light beam of the nanobubbles in the image of the light path, the spatial distribution of the scattered light intensity is integrated according to the Lambert-Beer law to infer the bubble concentration; The function-constrained algorithm and the unconstrained algorithm are used to estimate the nanobubble size parameters according to the set wavelength and scattered beam path image, and the nanobubble radius is inversely calculated. The scattering cross section is calculated using a light scattering algorithm, and the actual size of the bubble is inferred from the scattering beam diameter in the scattering beam path image; Constructing a model of light intensity, nanobubble water concentration and bubble radius in a light beam path image of nanobubbles based on the corresponding relationship between nanobubble water concentration and bubble radius according to the light scattering law; Step 400, calculating a dimensionless size parameter using the adjusted nanobubble diameter , and based on Mie scattering and Rayleigh scattering, a relationship between the scattered light intensity, nanobubble water concentration and nanobubble radius was constructed; in: Dimensionless size parameters , the relationship based on Mie scattering is: ; ; Dimensionless size parameters , the relationship based on Rayleigh scattering is: ; ; Where d is the adjusted nanobubble diameter; λ is the incident laser wavelength; is the radius of the nanobubble, in nanometers, Indicates the intensity of astigmatism; Indicates the concentration of nanobubble water; The volume of gas used to prepare nanobubble water on the ground, in milliliters; is the amount of nano bubble water prepared on the ground, in milliliters; A is a fixed value; , Represents the light coefficient.

2. The method for detecting nanobubble water concentration and nanobubble particle size based on light scattering according to claim 1, characterized in that: The error calculation formula between the theoretical scattered light intensity and the obtained scattered light intensity is set as: ;in, To calculate the error parameter; is the scattered light intensity measured in the experiment; is the theoretically calculated scattered light intensity; is the scattering angle; set the threshold value that makes the calculation error parameter converge, and use the least squares algorithm to calculate, and the calculation formula is: ;in, For the point The gradient at .

3. The method for detecting nanobubble water concentration and nanobubble particle size based on light scattering according to claim 1, characterized in that: In the process of constructing the relationship between the scattered light intensity, nanobubble water concentration and nanobubble diameter for detection based on light scattering, a verification formula for the nanobubble radius and nanobubble concentration is constructed, specifically: ; In the process of constructing the relationship between the scattered light intensity, nanobubble water concentration and nanobubble diameter for detection based on Rayleigh scattering, a verification formula for the scattered light intensity, nanobubble water concentration and nanobubble radius is constructed, specifically: ;in, and represent the refractive index of the scatterer and the medium respectively; is the radius of the nanobubble; is the bubble concentration.

4. The method for detecting nanobubble water concentration and nanobubble particle size based on light scattering according to claim 3, characterized in that: In dimensionless size parameters In the relationship based on Rayleigh scattering: By obtaining the scattered light intensity of lasers at different wavelengths, a set of equations for solving the radius of nanobubbles is established. The ratio of the scattered light intensity between any two adjacent different wavelengths is calculated as follows: ； in, and They represent the wavelengths of two adjacent lasers that have been arranged. and Indicates the corresponding scattered light intensity.

5. The method for detecting nanobubble water concentration and nanobubble particle size based on light scattering according to claim 2, characterized in that: Different algorithms are used to remove image noise from the acquired beam path image using median filtering and detect the beam boundary using the Canny edge detection operator, and to extract the light path profile; at the same time, the beam image of the acquired beam path image is normalized, and the value of the scattered light intensity of the image is read; Reverse detection verification was performed by constructing a relationship between the scattered light intensity, nanobubble water concentration and nanobubble radius for detection based on Mie scattering and Rayleigh scattering.

6. The method for detecting nanobubble water concentration and nanobubble particle size based on light scattering according to claim 1, characterized in that: In step 200, the scattered light intensity at multiple angles and the converted digital signal value are measured, and the specific calculation formula is: ; in, is an integer digital signal value; The maximum input light intensity of ADC for digital-to-analog conversion; The number of bits of the ADC used for digital-to-analog conversion.

7. The method for detecting nanobubble water concentration and nanobubble particle size based on light scattering according to claim 1, characterized in that: In step 300, the nanobubble water concentration and the nanobubble radius are processed using an unconstrained algorithm, and the specific calculation formula is: ; in, is the adjusted nanobubble diameter, is the extinction coefficient, is the scattered light intensity; is the rated light intensity of the incident laser, is the distance from the bubble to a point on the scattering surface.

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