A three-phase fluid saturation quantification method and system based on wet filling

Abstract

The present invention provides a three-phase fluid saturation quantification method and system based on wet filling, which relates to the field of environmental pollution. The method includes obtaining the measured light intensity of a sand box in a saturated water state and an unsaturated state; obtaining the measured light intensity of the sand box at the moment of pollutant infiltration; calculating the number of quartz sand particles filled in the residual water area of ​​the sand box in the unsaturated state; calculating the light absorption coefficient of the quartz sand; obtaining the spatial distribution of the number of quartz sand particles filled in the sand box and calculating the light intensity of the sand box in the residual water state; establishing a three-phase fluid saturation quantification model, calculating the light absorption coefficient of the pollutant by performing a mass balance between the actual and calculated pollutant injection amounts; calculating the light intensity of the sand box in the pollutant-saturated state, substituting it into the established three-phase fluid saturation model, and obtaining the saturation of each phase. The present invention can quantify the saturation of the three phases of pollutants, water, and air, and achieve quantitative characterization of the entire life cycle of pollutants leaking through the unsaturated groundwater zone to the aquifer.

Description

Technical Field

[0001] The present invention relates to the field of environmental pollution, and in particular to a three-phase fluid saturation quantification method and system based on wet filling. Background Art

[0002] The statements in this section merely provide background information related to the present invention and do not necessarily constitute prior art.

[0003] The leakage of non-aqueous liquid organic pollutants is the main cause of groundwater and soil pollution. They have low solubility in water and therefore form a long-term pollution source in groundwater. Once the hydrological conditions change, secondary pollution is very likely to occur, seriously threatening the ecological environment and human health. Pollutant leakage usually occurs on the surface or in shallow soil. The quantitative characterization of pollutants is crucial to the understanding of their migration patterns and the formulation of subsequent pollutant control plans. However, it is very difficult to quantitatively characterize pollutants in a three-phase system of pollutants, water, and air, which makes the control work after the leakage a very challenging task.

[0004] Currently, the main non-invasive quantitative analysis methods for contaminant migration within two-dimensional laboratory sandboxes include X-ray, gamma-ray, visible light transmission imaging, and high-density resistivity imaging. X-ray methods are expensive and pose safety risks during testing, significantly limiting their widespread application. High-density resistivity requires the determination of a standard curve for contaminant saturation and resistivity before use, significantly increasing the measurement workload and difficulty. Furthermore, due to the limited space of the sandbox used in laboratory experiments, boundary effects significantly affect the measurement results. Visible light transmission imaging is increasingly popular due to its ease of use, but it is currently typically applied to quantitative analysis of contaminant migration within saturated groundwater zones, i.e., within a two-phase system of contaminant and water. However, in actual spill scenarios, contaminants typically migrate from the unsaturated to the saturated zone of the soil. Exclusively considering the movement of the contaminant plume within the saturated zone will inevitably hinder the overall understanding of migration patterns.

[0005] Chinese invention patent application number CN201810407155.5 discloses a buried oil pipeline leakage diffusion migration experimental platform, but it cannot quantify the saturation of the oil spill pollution plume; MYDAlazaiza et al. quantitatively characterized the relationship between capillary force and water saturation based on a two-dimensional sand box in the paper [Characterization of Capillary Pressure–Saturation Relationships for Double-Porosity Medium Using Light Transmission Visualization Technique], but it is also only applicable to two-phase systems of water and gas; Chinese invention patent application number CN201410108042.7 discloses a method for quantitatively detecting the migration process and saturation of DNAPL, in which I oil / I s This value is calculated using the experimentally obtained light intensity values ​​for the DNAPL-saturated region and the light intensity values ​​for the initially saturated water region. Because DNAPL cannot completely fill the entire sandbox, this value ignores the impact of the heterogeneity of the quartz sand in the sandbox on the calculation results. Furthermore, the sandboxes used in the aforementioned schemes are all dry-packed, meaning the sandbox is first filled with quartz sand and then fully saturated with distilled water. However, sedimentation occurs during the dry sand saturation process, resulting in inconsistent positions of the quartz sand particles in the sandbox images obtained before and after water saturation, which in turn reduces the accuracy of saturation quantification. This also prevents the principles involved in the aforementioned scheme from being extended to quantify saturation in a three-phase system. Summary of the Invention

[0006] In order to address the shortcomings of the existing technology, the present invention provides a three-phase fluid saturation quantification method and system based on wet filling, which can quantify the three-phase saturation of pollutants, water, and air, and realize the quantitative characterization of the entire life cycle of pollutants leaking through the unsaturated zone of groundwater to the aquifer.

[0007] According to some embodiments, a first aspect of the present invention provides a method for quantifying saturation of a three-phase fluid based on wet loading, comprising:

[0008] Obtain the measured light intensity of the sand box in the water-saturated state and the measured light intensity of the sand box in the unsaturated state;

[0009] Inject pollutants and measure the light intensity in the sand box at the moment when the pollutants seep into the sand box;

[0010] According to the measured light intensity of the sand box in the water-saturated state and the measured light intensity of the sand box in the unsaturated state, the filling amount of quartz sand particles in the residual water area in the sand box in the unsaturated state is calculated;

[0011] Calculate the light absorption coefficient of quartz sand based on the number of quartz sand particles filled in the residual water area of ​​the sand box under unsaturated conditions;

[0012] According to the number of quartz sand particles filled in the residual water area in the sand box under unsaturated conditions and the light absorption coefficient of quartz sand, the spatial distribution of the number of quartz sand particles filled in the sand box is obtained, and the light intensity of the sand box under residual water conditions is calculated;

[0013] A three-phase fluid saturation quantification model was established, and the light absorption coefficient of the pollutants was calculated by performing mass balance on the actual injection amount and the calculated amount of pollutants.

[0014] The light intensity of the sand box under the saturated pollutant state is calculated and substituted into the established three-phase fluid saturation model to obtain the saturation of each phase.

[0015] Preferably, the filling amount of quartz sand particles in the residual water area in the sand box in the unsaturated state is calculated based on the light transmittance of the water-air interface, the measured light intensity of the sand box in the saturated water state, and the measured light intensity of the sand box in the unsaturated state.

[0016] Preferably, the light absorption coefficient of the quartz sand is calculated based on the average particle size of the quartz sand particles, the light transmittance of the interface between water and quartz sand, the measured light intensity corresponding to any two pixel points in the residual water area in the sand box in the unsaturated state under the saturated water state, and the filling number of quartz sand particles.

[0017] Preferably, the three-phase fluid saturation quantification model includes the three-phase fluid saturation in the residual water region, the three-phase fluid saturation in the capillary rise zone, and the three-phase fluid saturation in the saturated water region.

[0018] Preferably, the step of calculating the light absorption coefficient of the pollutant by performing mass balance on the actual injection amount and the calculated amount of the pollutant is as follows: first determine a pollutant injection moment, at which the plumes formed by the pollutants are all in the residual water area of ​​the unsaturated sand box, substitute the image light intensity at that moment and the derived expression of the relationship between the sand box light intensity in the saturated pollutant state and the sand box light intensity in the saturated water state into the calculation formula of the pollutant saturation in the residual water area, substitute the obtained pollutant saturation into the calculation formula of the pollutant amount to obtain the calculated amount of the pollutant, and compare the calculated amount of the pollutant with the actual injection amount of the pollutant at that moment to ensure that the two are consistent, and then obtain the light absorption coefficient of the pollutant.

[0019] Preferably, the light intensity of the sand box in the pollutant-saturated state is calculated based on the light absorption coefficient of the pollutant and the light intensity measurement value of the sand box in the water-saturated state.

[0020] Preferably, when obtaining the measured light intensity of the sand box in a saturated water state and the measured light intensity of the sand box in an unsaturated state, image correction is first performed, and the steps of the image correction are: first, an image is obtained when the sand box is in a saturated water state as a reference image, and two areas are selected on the reference image to be defined as calibration areas; the principle for determining the calibration area is that the area is in a completely water-saturated state during the unsaturated area formation stage and the subsequent pollutant migration stage, so the difference in light intensity in the calibration area in different images is caused by changes in the light source intensity; the light intensity of the image to be calibrated is multiplied by the corresponding calibration coefficient to obtain a corrected image, and the calibration coefficient is the ratio of the average light intensity of the calibration area of ​​the reference image to the average light intensity of the corresponding area of ​​the image to be calibrated; three consecutive frames are obtained at each image acquisition moment, and the average light intensity of the three images is used for quantitative calculation of saturation.

[0021] According to a second aspect of the present invention, a three-phase fluid saturation quantification system based on wet filling is provided, comprising a pollutant injection module, a liquid level control module, an image acquisition module, and a sand box; the pollutant injection module is connected to the sand box for injecting pollutants into the sand box; the liquid level control module is connected to the sand box for controlling the liquid level in the sand box; the image acquisition module comprises a light box arranged on the back of the sand box and a camera arranged on the front of the sand box for providing incident light and collecting measurement images; the quartz sand in the sand box is wet filled.

[0022] Preferably, the three-phase fluid saturation quantification system is set in a black box, using a light box as the only light source, a diffusion plate is used on the side adjacent to the sand box to uniformly transmit incident light, and the other surfaces are sealed.

[0023] Preferably, the sand box includes a porous medium cavity and a water trough, the water trough is arranged outside the porous medium cavity, and the porous medium cavity is provided with a connecting hole for maintaining hydraulic connection between the porous medium cavity and the water trough.

[0024] Compared with the prior art, the present invention has the following beneficial effects:

[0025] 1. The present invention is based on a wet-filled sand box, which can effectively avoid the saturation quantification error caused by the sedimentation of quartz sand when the dry-filled sand box is saturated with water, thereby improving the quantification accuracy of the three-phase fluid saturation; the filling medium in the sand box can be adjusted as needed, which can meet the needs of heterogeneity impact research.

[0026] 2. The present invention can quantify the three-phase fluid saturation of water, air, and pollutants in the sand box. The actual pollutant migration process in the soil usually involves a three-phase fluid system. Therefore, the present invention is more in line with the actual leakage scenario and has a broader application prospect compared with the traditional two-phase fluid saturation quantification method.

[0027] 3. The present invention only needs to obtain the light intensity under different states of the sand box and perform image processing according to the theoretical formula to obtain the spatial distribution of the three-phase fluid saturation in the sand box. It is a non-invasive measurement method with simple operation steps. Since the calculation process takes into account the influence of the heterogeneity of the quartz sand filled in the sand box on the quantitative results, it has high measurement accuracy and is applicable to a wide range of pollutant types.

[0028] Advantages of additional aspects of the present invention will be given in part in the following description and in part will be obvious from the following description, or will be learned through practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] The accompanying drawings, which constitute a part of the present invention, are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute improper limitations on the present invention.

[0030] Figure 1 is a flow chart of the method in Example 1;

[0031] Figure 2 This is a schematic diagram of the structure of the system in Example 2;

[0032] Figure 3 is a cross-sectional view of the light box on the xy plane in Example 2;

[0033] Figure 4 It is a cross-sectional view of the sand box on the xz plane in Example 2;

[0034] Figure 5 Schematic diagram of the obtained pollutant saturation quantification results.

[0035] Among them, 1. Black box; 2. Syringe pump; 3. Light box; 31. Aluminum profile; 32. Aluminum alloy plate; 33. LED light; 34. Diffuser plate; 35. Sand box bracket; 4. Sand box; 41. Porous medium cavity; 42. Water sink; 43. Connecting hole; 5. Digital camera; 6. Computer; 7. Camera bracket; 8. Peristaltic pump; 9. Water tank. DETAILED DESCRIPTION

[0036] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0037] Example 1

[0038] like Figure 1 As shown, the first embodiment of the present invention provides a three-phase fluid saturation quantification method based on wet filling, comprising the following steps:

[0039] S1. Obtain the measured light intensity of the sand box in a saturated water state and the measured light intensity of the sand box in an unsaturated water state;

[0040] S2. Inject pollutants and measure the light intensity in the sand box at the moment when the pollutants seep into the sand box;

[0041] S3. Calculate the number of quartz sand particles filled in the residual water area of ​​the sand box in the unsaturated state based on the measured light intensity of the sand box in the saturated state and the measured light intensity of the sand box in the unsaturated state;

[0042] S4. Calculate the light absorption coefficient of the quartz sand based on the number of quartz sand particles filled in the residual water area of ​​the sand box under unsaturated conditions;

[0043] S5. Obtain the spatial distribution of the number of quartz sand particles filled in the sand box according to the number of quartz sand particles filled in the residual water area in the sand box under an unsaturated state and the light absorption coefficient of the quartz sand, and calculate the light intensity of the sand box under the residual water state;

[0044] S6. Establish a three-phase fluid saturation quantification model, calculate the light absorption coefficient of the pollutant by performing mass balance on the actual injection amount and the calculated amount of the pollutant;

[0045] S7. Calculate the light intensity of the sand box under the saturated pollutant state, substitute it into the established three-phase fluid saturation model, and obtain the saturation of each phase.

[0046] In step S1, quartz sand is filled by wet method. First, the light intensity I of the sand box in the saturated water state is obtained by a digital camera. wt Then lower the liquid level of the sand box to the target level, and obtain the measured light intensity I of the sand box in the unsaturated state after the liquid level stabilizes. awt .

[0047] Quartz sand is loaded using a distributed filling method, with each loading height of 2-3 cm. During the filling process, the liquid level in the sand box is always 2 cm higher than the quartz sand filling height. After filling, the sand box is left to stand for 24 hours before measuring the light intensity in the saturated state. The light intensity is expressed as the grayscale value of the acquired image.

[0048] Before obtaining the measured light intensity of the sand box in an unsaturated state, the liquid level must be stable, and the liquid level stabilization time is 24 hours.

[0049] In step S2, pollutants are injected from the top of the sand box, and the light intensity I of the sand box is measured at different moments of pollutant infiltration. The time interval for obtaining the light intensity of the sand box during the pollutant injection stage is 1 minute, and the time interval for obtaining the light intensity of the sand box during the pollutant infiltration stage is 5 minutes.

[0050] In step S3, the theoretical expressions of the light intensity of the sand box in the saturated water state, saturated pollutant state and residual water state obtained based on Beer's law and Fresnel's law and the measured light intensity I of the sand box in the saturated water state obtained in steps S1 and S2 are wt and the measured light intensity I of the sand box in the unsaturated state awt, and obtain the filling quantity of quartz sand particles in the residual water area in the sand box under unsaturated state.

[0051] The theoretical expression of the light intensity of the sand box under saturated water state is:

[0052]

[0053] Where C is the geometric correction factor; I0 is the incident light intensity; τ ws is the light transmittance at the interface between water and quartz sand; α s is the light absorption coefficient of quartz sand; d s is the average particle size of quartz sand particles; α w is the light absorption coefficient of water; L is the thickness of the sand box; k is the number of quartz sand particles in the thickness direction of the sand box.

[0054] The theoretical expression of the light intensity of the sand box under the saturated pollutant state is:

[0055]

[0056] Among them, τ wo is the light transmittance at the interface between water and pollutants; α o is the light absorption coefficient of the pollutant; S wres is the residual water saturation of quartz sand.

[0057] The theoretical expression of the light intensity of the sand box under the residual water state is:

[0058]

[0059] Among them, τ wg is the light transmittance of the water-air interface; α g is the light absorption coefficient of air.

[0060] According to the theoretical expression of the light intensity of the sand box in the saturated water state and the theoretical expression of the light intensity of the sand box in the residual water state, the following expression can be obtained:

[0061]

[0062] Since the light absorption coefficient of quartz sand is much higher than that of water and air, the absorption of incident light intensity by the two can be ignored in the calculation. Equation (4) can be further expressed as:

[0063]

[0064] Among them, τ wg It can be calculated by the following formula:

[0065]

[0066] Among them, n wis the refractive index of water, which is 1.33; n g is the refractive index of air, which is 1.

[0067] By replacing the theoretical value in formula (5) with the measured value, the number of quartz sand particles filled in the residual water area in the sand box under unsaturated state can be obtained. The number of quartz sand particles filled in the residual water area in the sand box under unsaturated state k c It can be expressed as:

[0068]

[0069] In addition, the light intensity measurement values ​​of the sand box in the saturated water state and the unsaturated state need to be image corrected and then substituted into the above formula for calculation, so as to eliminate the influence of transient changes in incident light intensity on the calculation results.

[0070] Before quantitatively calculating the pollutant saturation, the acquired image needs to be corrected to eliminate the influence of transient changes in incident light intensity on the calculation results. The steps of image correction are as follows: First, an image is acquired when the sand box is in a saturated water state as a reference image. Two small areas (3×3cm 2 ) is defined as the "calibration area". The principle for determining the "calibration area" is that the area is in a completely water-saturated state during the unsaturated area formation stage and the subsequent dye white oil migration stage. Therefore, the difference in light intensity in the "calibration area" in different images is caused by changes in the light source intensity. The calibration coefficient is defined as the ratio of the average light intensity of the "calibration area" of the reference image to the average light intensity of the corresponding area of ​​the image to be calibrated. The corrected image can be obtained by multiplying the light intensity of the image to be calibrated by the corresponding calibration coefficient. Three consecutive frames are acquired at each image acquisition moment, and the average light intensity of the three images is used for quantitative calculation of saturation.

[0071] In step S4, two pixel points are randomly selected in the residual water area in the sand box under the unsaturated state. The theoretical light intensity I corresponding to these two points under the saturated water state is w1 and I w2 It can be expressed as:

[0072]

[0073]

[0074] Among them, k1 and k2 are the filling quantities of quartz sand particles corresponding to the two pixel points in the residual water area in the selected sand box.

[0075] After neglecting the light absorption coefficient of water, the ratio of the two can be expressed as:

[0076]

[0077] Substituting the measured light intensity corresponding to the two pixel points and the number of quartz sand particles filled in the residual water area in the sand box under unsaturated conditions into formula (10) can obtain the light absorption coefficient of quartz sand:

[0078]

[0079] Among them, I w1t , I w2t are the measured light intensities corresponding to any two pixel points in the residual water area in the selected sand box under the saturated water state.

[0080] In step S5, the spatial distribution k of the number of quartz sand particles filled in the sand box can be obtained by the number of quartz sand particles filled in the residual water area in the sand box under unsaturated state k c Combined with formula (11), the two selected pixel points should be located in the residual water area and the non-residual water area of ​​the sand box under the unsaturated state, respectively. The light intensity, the number of particles in the residual water area, and the light absorption coefficient of the quartz sand corresponding to these two pixel points under the saturated water state are all known values ​​at this time. Substituting them into formula (11) can obtain the number of quartz sand particles corresponding to the selected pixel point in the non-residual water area. Then, the next pixel point in the non-residual water area of ​​the sand box under the unsaturated state with an unknown number of quartz sand particles is selected for calculation. After traversing the non-residual water area pixel points in the unsaturated state, the spatial distribution of the number of quartz sand particles in the sand box can be obtained.

[0081] In addition, the light intensity of the sand box in the residual water state in step S5 is wres The measured light intensity I of the sand box in the saturated water state can be obtained by shifting the terms in formula (5) wt Substitute to obtain:

[0082]

[0083] In step S6, the three-phase fluid saturation and pore water distribution are divided into three parts: the residual water area, the capillary rise zone, and the saturated water area. Therefore, the three-phase fluid saturation quantification model includes the three-phase fluid saturation in the residual water area, the three-phase fluid saturation in the capillary rise zone, and the three-phase fluid saturation in the saturated water area.

[0084] Among them, the three-phase fluid saturations in the residual water region are expressed as:

[0085]

[0086] S wc =S wres (14)

[0087] S gc =1-S wc -S oc (15)

[0088] Among them, S oc is the pollutant saturation of the residual water area; S wc is the water saturation of the residual water area; S gc is the air saturation in the residual water area; S wres is the residual water saturation of the quartz sand, which is obtained by drying and weighing the quartz sand before filling the sand box.

[0089] The saturations of the three-phase fluids in the capillary rise zone are expressed as:

[0090]

[0091]

[0092]

[0093] S wm =1-S om -S gm (19)

[0094] Among them, S om S is the pollutant saturation in the capillary rise zone; wm is the water saturation in the capillary rise zone; S gm is the air saturation in the capillary rise zone; S g1 It is the effective gas saturation distribution in the sand box under unsaturated state.

[0095] The saturations of the three-phase fluids in the saturated water region are expressed as:

[0096]

[0097] S gb =0 (21)

[0098] S wb =1-S ob -S gb (twenty two)

[0099] Among them, S ob S is the pollutant saturation in the saturated water area; wb S is the water saturation in the gross saturated water area; gb is the air saturation in the saturated water area.

[0100] After establishing the three-phase fluid saturation quantification model, the light absorption coefficient of the pollutant is obtained by performing mass balance on the actual injection amount and the calculated amount of the pollutant.

[0101] The actual injection amount of pollutants can be calculated by the following formula:

[0102] V in =v in ·t in (twenty three)

[0103] Among them, v in is the pollutant injection rate; t in The duration of the pollutant injection.

[0104] The amount of pollutants can be calculated by the following formula:

[0105]

[0106] Among them, S o (x, z, t) is the pollutant saturation corresponding to the pixel point with coordinates (x, z) at time t; n1 and n2 are the number of pixels in the horizontal and vertical directions, respectively; A is the area corresponding to each pixel point; θ is the porosity of the quartz sand filled in the sand box.

[0107] Mass balance refers to balancing the calculated amount of pollutants in the residual water area at a certain moment and the actual injection amount to obtain the unknown number in the pollutant calculation formula, that is, the light absorption coefficient α of the pollutant. o .

[0108] The calculation formula for pollutant saturation in the residual water area is:

[0109]

[0110] Among them, I o Available through I w To express:

[0111]

[0112] Ignoring the light absorption coefficient of water, the above formula can be expressed as:

[0113]

[0114] Simplifying, we can get:

[0115]

[0116] In formula (28), only the light absorption coefficient α of the pollutant is o It is an unknown number.

[0117] The steps for obtaining the light absorption coefficient of the pollutant are as follows: first, determine a pollutant injection moment at which the plume formed by the pollutant is in the residual water area of ​​the unsaturated sand box. Substitute the image light intensity at that moment and formula (28) into formula (25) to obtain the pollutant saturation in the residual water area. Substitute the obtained pollutant saturation into the calculation formula of the pollutant to obtain V cal, and compare it with the actual amount of pollutant injected at that moment to ensure that the two are consistent, and then obtain V cal The unknown number contained in the equation is the light absorption coefficient α of the pollutant. o , and use this value in the subsequent three-phase saturation quantification calculation.

[0118] In step S7, the light intensity of the sand box under the saturated pollutant state is o The light absorption coefficient α of the pollutant o And the light intensity measurement value I of the sand box under saturated water state wt Perform the calculation:

[0119]

[0120] The calculated light intensity I of the sand box under the saturated pollutant state o By introducing the three-phase fluid saturation quantification model established in step S6, the quantitative result of the three-phase fluid saturation can be obtained.

[0121] The method for quantifying the saturation of a three-phase fluid provided in this embodiment is based on the principle of wet-filling a sand box. It can effectively avoid the saturation quantification error caused by the sedimentation of quartz sand when the sand box is saturated with water during dry-filling, thereby improving the measurement accuracy.

[0122] The three-phase fluid saturation quantification method provided in this embodiment can quantify the three-phase fluid saturation of water, air, and pollutants in the sand box. The actual pollutant migration process in the soil usually involves a three-phase fluid system. Therefore, the present invention is more in line with actual leakage scenarios and has broader application prospects compared with traditional two-phase fluid saturation quantification methods.

[0123] The method for quantifying three-phase fluid saturation provided in this embodiment simply requires acquiring light intensity at different states within a sandbox and performing image processing based on theoretical formulas to determine the spatial distribution of three-phase fluid saturation within the sandbox. This non-invasive measurement method is simple to use. Because the calculation process considers the impact of the heterogeneity of the quartz sand filling the sandbox on the quantification results, the method offers high measurement accuracy and is applicable to a wide range of pollutant types.

[0124] Example 2

[0125] This embodiment provides a three-phase fluid saturation quantification system based on wet filling. The system can use the method provided in the first embodiment to achieve accurate quantification of the saturation of the three-phase fluid.

[0126] like Figure 2As shown, the system mainly includes a pollutant injection module, a liquid level control module, an image acquisition module, and a sand box. The system is located in a black box 1, with a light box 3 as the only light source. The pollutant injection module is connected to the sand box and is used to inject pollutants into the sand box. It includes a syringe pump 2 and a selected pollutant, which in this embodiment is oil red O dyed white oil. The liquid level control module is connected to the sand box and is used to control the liquid level in the sand box. It includes a peristaltic pump 8 and a water tank 9. The image acquisition module includes a light box 3 set on the sand box and a camera 5 set on the side of the sand box, which is used to provide incident light and capture measurement images. The camera 5 is a digital camera connected to a computer 6 to transmit the acquired image data to the computer 6 for processing. The camera 5 is supported by a camera bracket 7 and is set on one side of the sand box 4.

[0127] like Figure 3 As shown, the light box 3 is constructed of aluminum profile 31. Except for the side adjacent to the sand box 4, which uses a diffusion plate 34 to evenly distribute the incident light of the LED lamp 33, the other sides use aluminum alloy plates 32 embedded in the grooves of the aluminum profile 31 to avoid light leakage. The sand box bracket 35 is used to place the sand box 4.

[0128] The cross-sectional view of the xz plane position of the sand box 4 is as follows Figure 4 As shown, the porous medium chamber 41 includes a porous medium chamber 41 and a water tank 42. The bottom of the porous medium chamber 41 is provided with a plurality of communication holes 43. The porous medium chamber 41 is used to be filled with experimental sand. The water tank 42 is connected to a peristaltic pump 8 to control the liquid level in the water tank 42. The communication holes 43 are used to maintain a hydraulic connection between the porous medium chamber 41 and the water tank 42, thereby ensuring that the free liquid surface height in the porous medium chamber 41 can be controlled by adjusting the liquid level in the water tank 42.

[0129] The sandbox was wet-packed with quartz sand, and camera 5 captured the measured light intensity of sandbox 4 in a saturated state. Peristaltic pump 8 lowered the liquid level in sandbox 4 to 10 cm. After the level stabilized, the measured light intensity of sandbox 4 in an unsaturated state was captured. Dyed white oil was injected from the top of the sandbox via syringe pump 2 at a rate of 0.5 mL / min for 50 minutes. Sandbox 4 was then left to rest for 48 hours to ensure adequate migration of the dyed white oil. Images were acquired every 1 minute during the dyed white oil injection phase, and every 5 minutes during the subsequent rest phase.

[0130] Before quantitatively calculating the saturation of dyed white oil, the acquired image needs to be corrected to eliminate the influence of transient changes in incident light intensity on the calculation results. The steps of image correction are as follows: First, an image is acquired when the sand box is in a saturated water state as a reference image. Two small areas (3×3 cm) are selected on the reference image. 2) is defined as the "calibration area". The principle for determining the "calibration area" is that the area is in a completely water-saturated state during the unsaturated area formation stage and the subsequent dye white oil migration stage. Therefore, the change in light intensity in the "calibration area" in different images is caused by the change in light source intensity. The calibration coefficient is defined as the ratio of the average light intensity of the "calibration area" of the reference image to the average light intensity of the corresponding area of ​​the image to be calibrated. The corrected image can be obtained by multiplying the light intensity of the image to be calibrated by the corresponding calibration coefficient. Three consecutive frames are acquired at each image acquisition moment, and the average light intensity of the three images is used for quantitative calculation of saturation.

[0131] Based on Beer's law and Fresnel's law, theoretical expressions for the light intensity in the sandbox under saturated water, contaminant-saturated, and residual water conditions can be derived. Combining these theoretical expressions with the measured light intensity in the sandbox under saturated water and unsaturated conditions, the number of quartz sand particles filling the residual water region within the sandbox under unsaturated conditions can be determined, and the light absorption coefficient of the quartz sand can then be calculated. Furthermore, using a constructed three-phase fluid saturation quantification model, the light absorption coefficient of the dyed white oil can be determined by performing a mass balance on the injected amount of dyed white oil. The light intensity in the sandbox under residual water and dyed white oil saturation conditions can be calculated, and the saturation of each phase can be determined using the established three-phase fluid saturation model. Figure 5 (a), (b), and (c) are the calculated spatial distributions of dyed white oil in the sand box at different times.

[0132] Example 3

[0133] The basic scheme of this embodiment is the same as that of the second embodiment, and the only difference is that when the sand box changes from a water-saturated state to an unsaturated state, the stable liquid level height of the sand box in this embodiment changes from 10 cm in the second embodiment to 15 cm. Figure 5 Figures (d), (e), and (f) show the spatial distribution of the dyed white oil within the sandbox at different times, as calculated in this example. This demonstrates the high accuracy of the pollutant saturation obtained by this method, enabling precise capture of differences in pollution plume migration behavior caused by changes in hydrogeological conditions. This provides a simple and widely applicable solution for the study of underground pollution plume migration.

[0134] The foregoing description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Those skilled in the art will readily appreciate that various modifications and variations of the present invention are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention are intended to be within the scope of protection of the present invention.

Claims

1. A three-phase fluid saturation quantification method based on wet filling, characterized in that: include: Obtain the measured light intensity of the sand box in the water-saturated state and the measured light intensity of the sand box in the unsaturated state; Inject pollutants and measure the light intensity in the sand box at the moment when the pollutants seep into the sand box; According to the measured light intensity of the sand box in the water-saturated state and the measured light intensity of the sand box in the unsaturated state, the filling amount of quartz sand particles in the residual water area in the sand box in the unsaturated state is calculated; Calculate the light absorption coefficient of quartz sand based on the number of quartz sand particles filled in the residual water area of ​​the sand box under unsaturated conditions; According to the number of quartz sand particles filled in the residual water area in the sand box under unsaturated conditions and the light absorption coefficient of quartz sand, the spatial distribution of the number of quartz sand particles filled in the sand box is obtained, and the light intensity of the sand box under residual water conditions is calculated; A three-phase fluid saturation quantification model was established, and the light absorption coefficient of the pollutants was calculated by performing mass balance on the actual injection amount and the calculated amount of pollutants. Calculate the light intensity of the sand box under the saturated pollutant state, substitute it into the established three-phase fluid saturation model, and obtain the saturation of each phase; Among them, the measurement light intensity of the sand box in the saturated water state and the measured light intensity of the sand box in the unsaturated state are obtained by wet filling quartz sand. First, the measured light intensity of the sand box in the saturated water state is obtained by a digital camera, and then the liquid level of the sand box is lowered to the target liquid level height. After the liquid level stabilizes, the measured light intensity of the sand box in the unsaturated state is obtained; The spatial distribution of the number of quartz sand particles filled in the sand box is obtained by traversing the pixel points in the non-residual water area in the sand box in an unsaturated state.

2. A three-phase fluid saturation quantification method based on wet filling according to claim 1, characterized in that: The filling amount of quartz sand particles in the residual water area in the sand box in the unsaturated state is calculated according to the light transmittance of the water-air interface, the measured light intensity of the sand box in the saturated water state, and the measured light intensity of the sand box in the unsaturated state.

3. The method for quantifying the saturation of a three-phase fluid based on wet filling according to claim 1, characterized in that: The light absorption coefficient of the quartz sand is calculated based on the average particle size of the quartz sand particles, the light transmittance of the interface between water and quartz sand, the measured light intensity corresponding to any two pixel points in the residual water area in the sand box in the unsaturated state and the saturated water state, and the number of quartz sand particles filled.

4. The method for quantifying the saturation of a three-phase fluid based on wet filling according to claim 1, characterized in that: The three-phase fluid saturation quantification model includes the three-phase fluid saturation in the residual water region, the three-phase fluid saturation in the capillary rise zone, and the three-phase fluid saturation in the saturated water region.

5. The method for quantifying the saturation of a three-phase fluid based on wet filling according to claim 4, characterized in that: The steps of calculating the light absorption coefficient of the pollutant by performing mass balance on the actual injection amount and the calculated amount of the pollutant are as follows: first, determine a pollutant injection moment, at which the plume formed by the pollutant is in the residual water area of ​​the unsaturated sand box, substitute the image light intensity at that moment and the derived expression of the relationship between the sand box light intensity in the saturated pollutant state and the sand box light intensity in the saturated water state into the calculation formula of the pollutant saturation in the residual water area, substitute the obtained pollutant saturation into the calculation formula of the pollutant amount to obtain the calculated amount of the pollutant, and compare the calculated amount of the pollutant with the actual injection amount of the pollutant at that moment to ensure that the two are consistent, and then obtain the light absorption coefficient of the pollutant.

6. The method for quantifying the saturation of a three-phase fluid based on wet filling according to claim 1, characterized in that: The light intensity of the sand box in the pollutant-saturated state is calculated based on the light absorption coefficient of the pollutant and the light intensity measurement value of the sand box in the water-saturated state.

7. The method for quantifying the saturation of a three-phase fluid based on wet filling according to claim 1, characterized in that: When obtaining the measured light intensity of the sand box in a saturated water state and the measured light intensity of the sand box in an unsaturated state, image correction is first performed. The steps of the image correction are: first, an image is obtained when the sand box is in a saturated water state as a reference image, and two areas are selected on the reference image to be defined as calibration areas; the principle for determining the calibration area is that the area is in a completely water-saturated state during the unsaturated area formation stage and the subsequent pollutant migration stage, so the difference in light intensity in the calibration area in different images is caused by the change in light source intensity; the light intensity of the image to be calibrated is multiplied by the corresponding calibration coefficient to obtain a corrected image, and the calibration coefficient is the ratio of the average light intensity of the calibration area of ​​the reference image to the average light intensity of the corresponding area of ​​the image to be calibrated; three consecutive frames are obtained at each image acquisition moment, and the average light intensity of the three images is used for quantitative saturation calculation.

8. A system for implementing the three-phase fluid saturation quantification method based on wet filling according to claim 1, characterized in that: It includes a pollutant injection module, a liquid level control module, an image acquisition module and a sand box; the pollutant injection module is connected to the sand box and is used to inject pollutants into the sand box; the liquid level control module is connected to the sand box and is used to control the liquid level height in the sand box; the image acquisition module includes a light box arranged on the back of the sand box and a camera arranged on the front of the sand box, which is used to provide incident light and collect measurement images; the quartz sand in the sand box is filled by wet method.

9. The system according to claim 8, wherein The system is set in a black box, using a light box as the only light source. A diffusion plate is used on the side of the light box adjacent to the sand box to evenly distribute the incident light, and the other sides are sealed.

10. The system according to claim 8, wherein The sand box includes a porous medium cavity and a water trough, wherein the water trough is arranged outside the porous medium cavity, and a connecting hole for maintaining hydraulic connection between the porous medium cavity and the water trough is provided on the porous medium cavity.

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