Petroleum pollution plume detection method and sampling device

Abstract

The invention relates to a petroleum pollution plume detection method and a sampling device, and provides a three-dimensional pollution field analysis technology based on directional stratified sampling aiming at efficient monitoring requirements of leakage pollution at a pipeline joint. The method comprises the steps of investigation area determination, radial survey line layout and optimization screening, vertical drilling and sheath tube installation, soil gas preliminary omnibearing collection, pollution abnormal point determination, directional layering secondary sampling and three-dimensional modeling, pollution migration analysis and source determination and the like. Radial measuring lines are arranged by taking a pipeline joint as a center, soil gas samples at different depths and directions are accurately collected by combining a layered directional sampling technology, a three-dimensional pollution distribution model is constructed, and three-dimensional depiction of pollution plumes and accurate positioning of a leakage source are realized; the sampling device supports multi-directional independent sampling at the same layer depth, gas mixing interference is avoided, and the detection precision and efficiency are remarkably improved.

Description

Technical Field

[0001] The present invention relates to the technical field of petroleum hydrocarbon pollution detection, and specifically relates to a method for detecting a petroleum pollution plume and a sampling device. Background Art

[0002] Petroleum plays a crucial role in the global economic and social development. With the rapid development of the petroleum industry, its impact on the environment and risks have been increasing year by year, becoming one of the important pollutants affecting the environment. Most crude oil and refined oil are transported by pipelines. However, with the increase in the operation time of pipelines, corrosion or man-made damage to pipeline lines and supporting storage equipment is likely to cause leakage of refined oil. At the same time, due to the small instantaneous leakage volume caused by corrosion and the small changes in the flow rate and pressure of gathering and transportation pipelines, it is not easy to be detected in time. Research shows that petroleum organic pollutants entering the soil will not only remain in the vadose zone, but also migrate downward into the aquifer, thus easily causing soil and groundwater pollution problems around pipelines and storage tanks.

[0003] Soil is a porous medium, and petroleum hydrocarbons exist in four forms in underground soil and water: gas phase, adsorbed phase, NAPL phase, and dissolved phase. Petroleum hydrocarbons contain a large amount of volatile organic compounds (VOCs), which are easily present in the gas phase. During migration, they enter soil pores and rise along the pores. Therefore, the study of the migration law of volatile organic compounds and the investigation of whether petroleum hydrocarbon soil pollution has occurred in the investigation site are the key links in the research of underground organic pollution, soil pollution remediation, and risk management, and also the requirements for determining soil pollution.

[0004] The soil gas method has become an important technical method for soil pollution site investigation and site risk assessment. Currently, relatively conventional soil investigation techniques include in-situ soil sampling and then sending it to a laboratory for testing. When applied in the field, systematic sampling methods, random sampling methods, etc. are mostly used, but the division of regions usually has a greater impact on the results. In the prior art, geophysical methods are also used to detect and monitor petroleum pollution. For example, the disclosed patents "201710502650X", "202411569756.8", etc. The physical property changes of contaminated soil and water that can be observed are reflected in electrical differences, such as resistivity, dielectric constant, etc. Usually, resistivity methods, transient electromagnetic methods, ground penetrating radar methods, and natural potential methods are used to detect the investigation area. However, there are certain limitations in quickly identifying pollution anomaly areas through the high-density electrical method. The high-density electrical method is not applicable to the situation of heterogeneous site hydrogeology, cannot truly depict the pollution plume, and has low accuracy.

[0005] In addition, in the study of pollutant migration, the anisotropy of the pore structure of the soil medium can lead to different degrees of concentration gradient differences of pollutants in different directions. Traditional soil gas sampling techniques, such as the stratified sampling techniques disclosed in "2021107167710", "2019205644056", etc., either only focus on the concentration distribution in the vertical dimension and ignore the spatial heterogeneity in the X-Y horizontal plane, or due to the connected design of the multi-directional sampling devices in the same layer, forced convection mixing occurs in the gas samples collected in different directions, which easily causes distortion of the detection data. The above technical limitations restrict the accurate analysis of the spatial characteristics of the pollution plume, thus directly affecting the accuracy of pollution source tracing and the reliability of risk assessment. Summary of the Invention

[0006] In view of this, the purpose of the present invention is to provide a method for detecting an oil pollution plume and a sampling device, which effectively solves the problems of insufficient spatial resolution of single-point vertical sampling, low azimuth sensitivity, and weak pollution source tracing ability during the detection of existing soil gas pollution.

[0007] To achieve the above purpose, the technical solution adopted by the present invention is: a method for detecting and monitoring oil pollution, characterized in that it includes the following steps: Step 1: Determine the investigation area and mark the positions of the pipeline joints. Step 2: Layout survey lines in the investigation area, radiate outward with the center of the pipeline joint as the center, arrange sampling points along the circumferential grid, and screen out the layout positions on both sides of the pipeline. Step 3: Drill to a set depth at the corresponding measuring points through a drilling device to ensure that the drilling width is adapted to the sampling device. Step 4: Conduct a preliminary all-round collection of the soil gas in the drill hole and record the sampling results. Step 5: According to the preliminary sampling results, delimit the measuring points with abnormal soil gas concentration and initially determine the corresponding positions as suspected pollution points. Step 6: Conduct secondary sampling on the suspected pollution points, including respectively collecting the soil gas at each depth position towards and perpendicular to the azimuth of the center of the pipeline joint one by one and recording the results; after all the suspected pollution points are sampled according to the method described in this step, outline the three-dimensional soil gas pollution distribution based on the detection results of the soil gas concentration. Step 7: Based on the three-dimensional soil gas pollution distribution, conduct a single-hole concentration difference determination, predict the migration trend of the pollutant according to the determination result, and determine the distribution range of the pollution plume; then compare the soil gas concentration results of adjacent suspected pollution points to determine the location of the pollution source.

[0008] Further, in step 3, a hollow auger is used to drill a vertical hole to a predetermined depth, and a PVC casing pipe is immediately inserted after drilling, and the bottom is sealed to prevent air from mixing in.

[0009] Further, in step 5, before sampling, undisturbed points at the edge of the investigation are selected as references, and the normal values of the pollutant background concentrations at each reference point are calculated. Then, the concentration results obtained at each sampling point are compared with the normal values of the background concentrations at the reference points, and the areas exceeding 3 times the standard deviation of the background value or showing a gradient increase at multiple consecutive points are marked as suspected pollution points.

[0010] Further, in step 6, the drill hole in the suspected pollution point is advanced step by step according to the preset layer depth, and soil gas samples are collected in the directions facing and perpendicular to the center of the pipe connection respectively, and the three-dimensional coordinates and environmental parameters are recorded, and the pollutant concentrations in the samples are analyzed; then, based on the Kriging interpolation method, the discrete sampling point data is converted into a continuous concentration field, four independent three-dimensional pollution cloud maps are generated, and a comprehensive three-dimensional concentration gradient tensor field is synthesized through vector superposition.

[0011] Further, after sampling in the drill hole of the suspected pollution point, a single-hole concentration difference determination is first carried out, and the determination rule is: taking the pipe flange connection as the coordinate origin, if the concentration on the east side is higher than that on the west side, it indicates that the pollutant migrates in the east-west direction, and then the underground water flow direction data is combined to verify whether the migration direction is consistent with the water flow direction; based on the concentration data of adjacent measuring points, a horizontal concentration distribution map is generated by using the Kriging interpolation method, and the concentration gradient change rate is calculated; when the gradient change rate > 15% / m, it is marked as the advancing direction of the pollution front to realize the determination of the lateral pollution plume expansion; then, the concentration differences at different depth layers are compared. If the concentration in the shallow layer is higher than that in the deep layer, it indicates that the pollution source is close to the ground surface and there is a risk of shallow leakage of the pipeline; the spatial distances between the concentration peaks of all abnormal points and the flange node are statistically analyzed. If more than 80% of the peak points are distributed within the investigation area of the target flange point and the concentration decay with distance conforms to the exponential model, then it is determined that the flange connection is the leakage source.

[0012] The present invention also provides an oil pollution plume sampling device, which includes a sampling cylinder, an adjustment assembly and a positioning assembly. The cylinder wall of the sampling cylinder is provided with an air inlet group at intervals along its length direction. Each air inlet group includes a plurality of air inlets communicating with the inner cavity of the sampling cylinder; the adjustment assembly includes a base plate, a central shaft and an adjustment seat. The central shaft is concentrically and slidably sleeved in the sampling cylinder. A base plate is slidably sleeved on the central shaft. The adjustment seat is rotatably sleeved on the central shaft. The bottom of the adjustment seat is fixed to the top surface of the base plate. A top spring is provided between the top of the adjustment seat and the top plate at the top of the central shaft; the bottom of the central shaft extends below the base plate and is fixed with a conical head. Grooves are symmetrically opened on the two side walls of the conical head; centered on the conical head, the positioning assembly is arranged around it. The positioning assembly includes a positioning seat, a gas sampling pipe and an arc-shaped baffle. The positioning seat is fixed on the base plate. The gas sampling pipe is slidably installed on the positioning seat through a sliding sleeve. A ball seat is fixed at the inner end of the gas sampling pipe. A spring is provided between the ball seat and the positioning seat. An arc-shaped baffle is fixedly sleeved at the outer end of the gas sampling pipe; the gas sampling port at the end of the gas sampling pipe corresponds to the air inlet on the sampling cylinder. The output port of the gas sampling pipe is communicated with a sample collection assembly on the ground through a gas guide pipe.

[0013] Further, the positioning seat is fixed on the base plate. A sliding sleeve is fixedly sleeved on the positioning seat. The gas sampling pipe is slidably sleeved in the sliding sleeve. The gas sampling pipe is provided with a positioning hole. An exhaust port is opened at a position corresponding to the positioning hole on the sliding sleeve. A gas guide pipe is hermetically connected to the exhaust port.

[0014] Further, the sample collection assembly includes a gas guide pipe, an air pump and a sample collection bag. One end of the gas guide pipe is hermetically connected to the output port on the sliding sleeve. A one-way valve is also provided on the gas guide pipe. The other end of the gas guide pipe passes through the sampling cylinder and is communicated with the sample collection bag through the air pump to collect the soil gas collected.

[0015] The beneficial effects of the above technical solutions are as follows: An oil pollution plume detection method and sampling device provided by the present invention focus on high-risk leakage areas, radiate survey lines outward with the pipe connection as the center, screen the point positions on both sides of the pipe along the circumferential grid, concentrate on detecting the sources around the most likely leakage connection, reduce the ineffective detection area, save the detection time and labor cost, and improve the scientificity and rationality of the detection work.

[0016] In the secondary sampling stage, for each suspicious drilling point, gas samples in the same depth towards the center of the pipe connection and perpendicular to its direction are collected respectively, breaking through the limitation of traditional single-direction sampling. By collecting samples in different directions respectively, the concentration gradient difference in the horizontal direction is obtained, the pollutant diffusion characteristics are clearly grasped, and at the same time, gas mixing is prevented to ensure the authenticity and reliability of the samples. Then, combined with the vertical depth data, a three-dimensional pollution distribution model is constructed to intuitively present the shape of the pollution plume and provide a scientific basis for pollution control.

[0017] The present invention uses Kriging interpolation method to process multi-directional stratified sampling data, generates a three-dimensional pollution cloud map, and vectorially superimposes and synthesizes a comprehensive three-dimensional concentration gradient tensor field, converting discrete sampling data into a continuous three-dimensional model to clearly display the spatial distribution of the pollution plume and assist in decision-making; through the three-dimensional concentration gradient tensor field, accurately judge the diffusion direction and intensity of pollutants, and integrate multiple groups of data and spatial analysis methods to make the pollution assessment more scientific and comprehensive and improve the credibility of the results.

[0018] And taking the flange connection as the coordinate origin, by comparing the concentration differences in different directions of a single hole and combining with the underground water flow direction, etc., determine the migration direction; statistically analyze the peak value distribution of the concentration at abnormal points, and integrate multiple factors and data statistics to improve the accuracy of pollution source location and avoid ineffective treatment caused by misjudgment.

[0019] The three-dimensional multi-directional independent sampling method proposed in this study realizes the independent capture of pore gases in each main direction of a specific depth layer by constructing a non-connected directional sampling channel array, effectively analyzes the migration path and source strength position of pollutants in three-dimensional space. This method breaks through the limitation of the traditional sampling technology on the spatial analysis ability of the pollution plume and provides a reliable technical means for pollution source tracing under complex geological conditions.

[0020] The sampling device provided by the present invention samples gases in groups in different directions to obtain comprehensive data, providing a basis for the construction of a three-dimensional model. The design of multiple air inlets in one group realizes gas sampling in different directions in the borehole, improves the sampling efficiency, and the inclined air inlets reduce the entry of soil particles and improve the purity of gas samples; the conical bottom adapts to soils at different depths to ensure smooth sampling; through the adjustment component, it can flexibly switch the sampling direction and the sampling perpendicular to the center of the connection to avoid gas mixing and improve the accuracy of samples; through the cooperation of the adjustment component and the positioning component, it can stably sample at different depths and directions, optimize the operation process, reduce cumbersome steps, improve the sampling efficiency, and reduce the labor intensity.

[0021] The present invention provides a method and a sampling device for detecting an oil pollution plume. Radial survey lines are arranged centered on the pipeline connection, and combined with the stratified directional sampling technology, soil gas samples at different depths and directions are accurately collected to construct a three-dimensional pollution distribution model to realize the three-dimensional characterization of the pollution plume and the precise positioning of the leakage source; the sampling device of the present invention supports multi-directional independent sampling at the same layer depth, avoids gas mixing interference, and significantly improves the detection accuracy and efficiency. Brief Description of the Drawings

[0022] Figure 1 It is a flow chart of the method for detecting an oil pollution plume of the present invention; Figure 2 It is a schematic diagram of the distribution structure of pollutants in underground soil; Figure 3 It is a schematic diagram of the layout structure of sampling points; Figure 4 Schematic diagram of the division structure for different sampling orientations at each sampling point; Figure 5 Schematic diagram of the external structure of the sampling cylinder; Figure 6 Schematic diagram of the internal sectional structure of the sampling cylinder; Figure 7 Schematic diagram of the three-dimensional structure of the positioning gas sampling assembly; Figure 8 Schematic diagram of the sectional structure of the positioning assembly.

[0023] Reference numerals: 1 - sampling cylinder, 2 - adjusting assembly, 21 - adjusting seat, 22 - top plate, 23 - central axis, 24 - top spring, 25 - base plate, 3 - positioning gas sampling assembly, 31 - conical head, 32 - positioning assembly, 321 - baffle, 322 - positioning seat, 323 - gas sampling pipe, 324 - sliding sleeve, 325 - spring, 326 - top head, 327 - output port, 328 - gas sampling port, 329 - exhaust port, 4 - intake port, 5 - connecting flange, 6 - sampling point, 7 - pipeline. Specific embodiments

[0024] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments: Embodiment 1. This embodiment aims to provide a method for detecting petroleum pollution plumes. Leakage from underground storage tanks and pipelines is an important source of petroleum hydrocarbon pollution in soil and groundwater. Leakage pollution from petroleum pipelines is a common hidden danger threatening the ecological environment. Among them, connection parts such as flanges and valves are vulnerable areas with the highest leakage incidence due to long-term mechanical vibration, corrosion and other factors, which in turn lead to the migration and diffusion of petroleum pollutants along soil pores, forming hidden underground pollution plumes. Existing monitoring technologies generally adopt a combination of grid-based sampling and layered soil sampling. Although pollutant concentration data at different depths can be obtained, only gas samples with mixed orientations can be obtained at the same borehole depth, and the concentration gradient differences of pollutants in the horizontal direction cannot be distinguished. This lack of spatial resolution makes it difficult to accurately judge the migration path and diffusion range of pollutants. Especially in scenarios with obvious directional leakage characteristics such as pipeline connections, it is easy to misjudge or miss the pollution source.

[0025] Therefore, this embodiment provides a method for detecting petroleum pollution plumes based on central radiation monitoring at the connection, which adopts a three-dimensional multi-directional independent sampling method to achieve independent capture of pore gases corresponding to each main orientation in different soil depths, thereby effectively analyzing the migration path and source strength position of pollutants in three-dimensional space, and providing a reliable technical means for pollution source tracing under complex geological conditions. When the method for detecting petroleum pollution plumes provided in this embodiment is actually applied, as Figure 1-4 shown, it includes the following steps: Step 1: Determine the investigation area; Based on the pipeline routing map, combined with on-site reconnaissance, use RTK-GPS or total station to determine the boundary of the investigation area to ensure coverage of the area around the pipeline connection points; Then use a metal detector and a pipeline locator to accurately locate the coordinates of the flange connection points, mark them as potential high-risk leakage points, and record the material, service life, and historical maintenance records of the connection points at the same time.

[0026] Step 2: Layout of survey lines; As Figure 3 shown, layout survey lines within the investigation area, radiating outward from the center of the pipeline connection, and arrange sampling points along the circumferential grid, that is, first set the main survey lines along the pipeline direction and its perpendicular direction, and the remaining survey lines are evenly distributed to form a circumferential grid, and increase the sampling points near the pipeline connection to capture high-concentration leakage signals; Then spread outward to form a diffusion-type sampling point layout pattern from dense to sparse. Finally, screen the sampling point positions on both sides of the pipeline, use a pipeline locator to accurately locate the pipeline direction, and eliminate the sampling points that coincide with the pipeline position to avoid damage to the pipeline during drilling construction. Further, for convenient recording, the selected sampling points can also be numbered to generate a survey line layout map and a sampling point distribution map.

[0027] Step 3: Drilling operation; Based on the positions of the sampling points arranged in Step 2 above, use a hollow auger drill to drill vertically to the preset depth, ensure that the drilling width is adapted to the sampling device, and after the drilling is completed, immediately insert a PVC casing tube with an inner diameter adapted to the sampling device, and seal the bottom with a highly expandable and corrosion-resistant sealing material, such as a silicone rubber seal ring, etc., to prevent the mixing of the atmosphere and affect the accuracy of the sample.

[0028] Step 4: Preliminary all-round collection of soil gas; Conduct preliminary all-round collection of soil gas in each borehole and record the sampling results; In this step, existing commonly used soil gas sampling equipment can be selected, such as a sampling system combining a vacuum pump and a Teflon gas bag, or a hand-held or electric soil gas sampler. The core component includes a telescopic sampling probe with an airbag or a micro pump, which is connected to a ground controller through a hose. Slowly lower the sampling probe to the bottom of the borehole, start the vacuum pump, extract the mixed gas in the borehole, and continuously sample for 5 minutes to ensure that the gas bag is full. After the sampling is completed, a portable gas analyzer can be used on-site to quickly qualitatively and semi-quantitatively analyze the collected soil, measure the concentration of characteristic components of petroleum pollutants, and record the results to form a preliminary sampling result database to provide data support for the subsequent delineation of suspected pollution points. This step is only a preliminary sampling, aiming at rapid screening, without distinguishing soil gas at different depths or orientations, and only obtaining the concentration of the mixed gas in the borehole. During the sampling process, it is necessary to avoid the mixing of the atmosphere and ensure good airtightness of the gas bag.

[0029] Step 5: Demarcate suspected pollution points; Before the preliminary sampling in Step 4, select 3 - 5 representative points on the edge of the investigation area that are not disturbed by pipeline leakage, have stable soil properties as reference points, obtain the pollutant background concentration data using the same sampling method, conduct statistical analysis on the reference point data, calculate the average value and standard deviation of each pollutant component, and construct the normal value range of the background concentration. Then compare the concentration results of each sampling point in Step 4 with the normal value of the reference point background concentration. When the pollutant concentration at the sampling point exceeds 3 times the standard deviation of the background value, or shows a gradient increase trend at multiple consecutive points with an increase amplitude exceeding 2 times the background value, determine that the sampling point is a suspected pollution point, and at the same time record key parameters such as the geographical coordinates, depth information, and concentration peak value of the suspected pollution point for secondary sampling of the suspected pollution point.

[0030] Step 6: Directional stratified secondary sampling; Use the sampling device to conduct secondary sampling on each suspected pollution point. As Figure 4 shown, it includes collecting the soil gas at each depth position towards and perpendicular to the center azimuth of the pipeline connection respectively and recording the results. Specifically, for each suspected pollution point, divide the soil depth into multiple layers to more precisely capture the concentration change of pollutants in the vertical direction. Collect samples layer by layer from top to bottom in the borehole according to the preset layer depth, and first collect the shallow layer and gradually probe down to the target depth to achieve step-by-step sampling. At each preset stratified depth, direct the sampling probe towards the center position of the pipeline connection and sample perpendicular to the center azimuth of the connection to ensure the accuracy of the sampling direction. Then start the sampling device and slowly extract the soil gas sample in this direction according to the preset sampling volume and sampling speed. During the sampling process, monitor parameters such as the pressure change and gas flow rate of the sampling system in real time to ensure the stability of the sampling process and the integrity of the sample. By collecting the soil gas samples towards and perpendicular to the center azimuth of the connection at different depths respectively, it provides basic data for subsequent analysis of the diffusion characteristics of pollutants in the horizontal direction.

[0031] After analyzing the above-sampled samples, the concentration data of each layer and each azimuth are associated with their three-dimensional coordinates to construct a discrete point data set. Then, based on the distribution characteristics of the sampling point data and the spatial variability of the pollutant concentration, the Kriging interpolation method is used to perform spatial interpolation on the integrated discrete sampling point data to obtain the continuous concentration field data in the horizontal and vertical directions. Four independent three-dimensional pollution cloud maps are constructed using 3D modeling software. Each group of three-dimensional pollution cloud maps corresponds to the pollutant concentration distribution with different diffusion characteristics, such as towards the center of the connection and perpendicular to the center of the connection. During the modeling process, the concentration data is mapped into a three-dimensional space grid, and through visualization means such as color gradient and isosurface rendering, the concentration change trend and distribution range of pollutants at different depths and in different directions are intuitively displayed, that is, the high-concentration areas and the boundaries with significant concentration gradient changes are marked, and the spatial shape of the pollution plume is initially outlined.

[0032] Furthermore, in practical applications, the four independent three-dimensional pollution cloud maps can also be vectorially superimposed to synthesize a comprehensive three-dimensional concentration gradient tensor field. This process integrates the concentration gradient information in different directions through mathematical operations to form a comprehensive model that comprehensively describes the three-dimensional spatial distribution characteristics of pollutants. When performing vector superposition, the magnitude and direction of the concentration gradient in each direction are fully considered, and using tensor mathematics theory, the gradient components in each direction are combined into a three-dimensional tensor field. This tensor field can not only clearly present the overall shape and range of the pollution plume, but also accurately reflect the diffusion intensity and migration trend of pollutants in different directions, providing a more accurate and comprehensive basis for subsequent pollution source location and pollution range determination.

[0033] Step 7: Pollution migration analysis and source location; Based on the three-dimensional soil gas pollution distribution generated in the above steps and combined with the relative position relationship between each sampling point and the pipeline flange connection, in this step, through multi-dimensional data fusion and spatial correlation analysis, the accurate analysis of the pollutant migration path and the reliable location of the leakage source are realized.

[0034] In a specific implementation manner, first, based on the single-hole stratified sampling data, the concentration differences between the main axial direction (towards the pipeline connection) and the vertical axial direction at different depths within the same borehole are analyzed. If the concentration in the main axial direction is more than 20% higher than that in the vertical axial direction, it indicates that the pollutants mainly migrate along the pipeline axis; if the concentration in the shallow layer within the borehole is significantly higher than that in the deep layer, it suggests that the leakage point may be close to the surface or there is continuous leakage. To further verify the migration mechanism, such as Figure 2As shown, in fact, the groundwater flow direction can also be compared and verified with the analysis results of the concentration difference of a single hole. If the two point in the same direction, the credibility of the judgment of the migration direction can be enhanced. In actual application, physical simulation experiments can be carried out using soil columns, sand box models, etc. (this is the existing technology and will not be elaborated here) to further detect characteristic parameters such as the migration front of petroleum hydrocarbon pollutants, pollutant concentration, and groundwater level, and to carry out the distribution characteristics and migration and transformation laws of typical petroleum hydrocarbon pollutants under different formation lithologies, lithological combinations, and groundwater levels, so as to more accurately depict the detection results of soil and groundwater petroleum hydrocarbon pollution in the polluted site; if they are inconsistent, other factors such as soil porosity and the nature of the pollutants themselves need to be comprehensively considered to further analyze whether there are multiple diffusion mechanisms or local abnormal conditions affecting the judgment of the migration direction.

[0035] Then, using the above three-dimensional pollution cloud map, extract the concentration gradient change rate and isoconcentration surface information: on the horizontal plane, identify the frontal area where the gradient change rate > 15% / m, which marks the active diffusion front of the pollution plume; vertically, analyze the concentration attenuation rate. If the attenuation rate from the shallow layer to the deep layer > 30%, it is determined that the pollution plume mainly diffuses horizontally. By selecting 3 - 5 times the background concentration value as the threshold, generate a three-dimensional model of the isoconcentration surface. By superimposing the gradient front and the isoconcentration surface, the high-concentration core area and the low-concentration transition zone can also be distinguished, so as to clarify the three-dimensional space range of the pollution plume.

[0036] After determining the spatial range of the pollution plume, lock the leakage source through peak concentration clustering analysis and multi-point horizontal comparison; that is, count the peak concentrations of all suspected pollution points. If more than 80% of the peak points are densely distributed within 10 meters around the pipe connection and the concentration decays exponentially with distance, it can be initially determined that the connection is a potential leakage source; combined with the concentration data of adjacent measurement points, if the distribution of high-concentration points is consistent with the pipeline trend and groundwater flow direction, it further supports the determination of the leakage source; otherwise, interference factors such as surface leakage or historical pollution need to be investigated. Finally, through close-range dense sampling and non-destructive testing of the pipeline, such as ultrasonic wall thickness measurement, conduct on-site verification. If physical evidence such as corrosion perforation or seal failure is found at the pipe connection, the leakage source can be confirmed.

[0037] This step breaks through the limitations of traditional single-concentration discrimination through the triple criteria of "directionality - gradient - spatiality", distinguishes pipeline leakage from background pollution through concentration comparison at different depths and corresponding azimuth positions, avoids interference from non-related signals, combines frontal recognition and isoconcentration surface analysis, accurately quantifies the diffusion range and intensity of the pollution plume, and finally uses peak clustering and attenuation models to convert discrete data into spatially correlated evidence, improving the reliability of source location, thus providing key technical support for the efficient treatment of petroleum pipeline leakage pollution.

[0038] The oil pollution plume detection method provided in this embodiment arranges radial survey lines with the pipe connection as the center. After initially screening to determine abnormal points, in the secondary sampling stage, using the multi-directional layered sampling technique, for each suspicious borehole point, gas samples are collected in the same depth in the directions towards the center of the pipe connection and perpendicular directions respectively. By comparing the concentration differences in different directions, a three-dimensional pollution distribution model is constructed. This spatial orientation sampling mechanism breaks through the spatial mixing limitation of traditional methods, can accurately capture the diffusion characteristics of pollutants in the horizontal direction, and combined with vertical depth data, can clearly outline the three-dimensional shape of the pollution plume, providing a reliable basis for tracing the leakage path and locating the pollution source, and significantly improving the detection efficiency and pollution assessment accuracy.

[0039] Embodiment 2, based on Embodiment 1, this embodiment provides an oil pollution plume sampling device, which is applied to the secondary sampling in Step 6 of the oil pollution plume detection method described in Embodiment 1.

[0040] As Figure 5-8 shown, the oil pollution plume sampling device in this embodiment includes a sampling cylinder 1, an adjustment component 2, and a positioning component 32. The barrel wall of the sampling cylinder 1 is provided with an air inlet group at intervals along its length direction. Each air inlet group includes a plurality of air inlets 4 communicating with the inner cavity of the sampling cylinder 1, and each air inlet 4 is inclined downward. In this embodiment, each group of air inlets 4 includes four air inlets 4, representing sampling of soil gas in different directions in the borehole. The bottom of the sampling cylinder 1 is in a conical structure.

[0041] In this embodiment, the adjustment component 2 includes a base plate 25, a central shaft 23, and an adjustment seat 21. As Figure 6 shown, the central shaft 23 is concentrically and slidably sleeved in the sampling cylinder 1. A base plate 25 is slidably sleeved on the central shaft 23. The adjustment seat 21 is rotatably sleeved on the central shaft 23. In this embodiment, the adjustment seat 21 is in a columnar structure, and its outer diameter is adapted to the through hole on the top cover of the sampling cylinder 1. The adjustment seat 21 extends vertically upward out of the sampling cylinder 1. The top of the central shaft 23 is vertically and fixedly provided with a top plate 22 in the horizontal direction. And a top spring 24 is provided between the top of the adjustment seat 21 and the top plate 22 at the top of the central shaft 23. The bottom of the adjustment seat 21 extends into the sampling cylinder 1 and is fixedly connected to the top surface of the base plate 25. The bottom of the central shaft 23 passes through the adjustment seat 21 and extends below the base plate 25, and its end is fixedly provided with a tapered head 31. As Figure 7 shown, two opposite side walls of the tapered head 31 are symmetrically provided with grooves for adapting to the arc-shaped top head 326 at the end of the gas collecting pipe 323, so as to drive the positioning component 32 to extend out for collecting soil gas or block the collection port by avoidance.

[0042] As Figure 7As shown in the figure, with the conical head 31 as the center, the positioning components 32 are arranged around it. In this embodiment, there are four groups of positioning components 32, which are respectively opposite to the positions of the air inlets 4 in four directions on the sampling cylinder 1, so as to facilitate sampling of soil gas facing or perpendicular to the flange connection of the pipeline 7 in pairs. For example, when collecting the soil gas facing the flange connection of the pipeline 7 at this depth, the air inlet 4 perpendicular to the flange connection is blocked at this time to avoid gas mixing, and vice versa.

[0043] In the specific implementation structure, as Figure 7 and 8 shown, the positioning component 32 includes a positioning seat 322, a sampling pipe 323 and an arc-shaped baffle 321. The positioning seat 322 is fixed on the substrate 25 in an L-shaped structure. A sliding sleeve 324 is fixedly installed in the positioning seat 322. The sampling pipe 323 is slidably sleeved in the sliding sleeve 324, and an arc-shaped top head 326 is also fixed at one end of the sampling pipe 323 close to the conical head 31. A spring 325 is sleeved on the sampling pipe 323 between the arc-shaped top head 326 and the sliding sleeve 324. An arc-shaped baffle 321 is fixedly sleeved at one end of the sampling pipe 323 far from the conical head 31, and the inner cavity of the sampling pipe 323 is hollow, and a sampling port 328 is provided at the outer end. After the sampling port 328 is communicated with the air inlet 4 on the barrel wall of the sampling cylinder 1, the soil gas can flow along the air inlet 4 to the sampling port 328 through the sample collection component, and is sampled to the ground through the output port 327 provided on the sliding sleeve 324.

[0044] Furthermore, as Figure 8 shown, in this embodiment, an output port 327 is also provided on the side wall of the sliding sleeve 324. An external sample collection bag is connected to the output port 327 through a conduit. An exhaust port 329 is opened on the side wall of the sampling cylinder 1. When the output port 327 is communicated with the exhaust port 329, the soil gas at this position can be collected from the sampling pipe 323 to the sample collection bag through the conduit on the output port 327. In this embodiment, the sample collection component includes a conduit, an air pump and a sample collection bag. One end of the conduit is hermetically connected to the output port 327 on the sliding sleeve 324, and a one-way valve is also provided on the conduit. The other end of the conduit passes through the sampling cylinder 1 and is communicated with the sample collection bag through the air pump to collect the sampled soil gas. In actual use, the soil gas collected at different depths and different orientations is numbered respectively to facilitate the analysis of the soil gas concentration at each position.

[0045] In fact, in this embodiment, through the cooperation of the positioning component 32 and the conical head 31, soil gas can be collected at different depths and in different orientations. After the sampling tube is lowered to a set depth in the borehole, by rotating the top plate 22 on the central shaft 23, the conical head 31 at the bottom of the central shaft 23 can be driven to rotate, so that the groove on the conical head 31 corresponds to the arc-shaped head 326 in the left-right direction. Then, by pressing the top plate 22 to drive the conical head 31 to move vertically downward, at this time, the arc-shaped heads 326 on the front and rear sides can slide along the wall surface of the conical head 31, so that the spring 325 is compressed, and the gas collection cylinder moves outward in the sleeve, so that the exhaust port 329 on the gas collection cylinder does not correspond and communicate with the output port 327 on the sliding sleeve 324. At the same time, the arc-shaped baffle 321 tightly presses against the side wall of the sampling cylinder 1, so that the soil gas in the front-back direction will not be collected and cannot enter the sample collection bag through the gas guide pipe. At this time, since the heads 326 in the left-right direction are located in the grooves, the springs 325 on the left-right gas collection cylinders are not compressed, and the arc-shaped baffle 321 contacts the inner wall of the sampling cylinder 1. The gas intake ports 328 on the left-right gas collection cylinders communicate with the gas intake port 4 on the sampling cylinder 1, and at the same time, the exhaust port 329 on the gas collection cylinder corresponds and communicates with the output port 327 on the sliding sleeve 324. The soil gas in the left-right direction at this layer can be collected into the sample collection bag through the gas guide pipe. Then, after the soil gas in the left-right direction is collected, under the action of the top spring 24, the top plate 22 drives the central shaft 23 to drive the conical head 31 to reset, and then the central shaft 23 is rotated to turn the orientation of the groove on the conical head 31, and the soil gas in the front-back direction is collected by the same method. In this way, by controlling the lowering depth of the adjusting component 2 in the sampling cylinder 1, the whole-process soil gas collection at different depths and in different orientations in the borehole can be realized.

[0046] Working principle description; For the oil pollution plume sampling device provided in this embodiment, during actual application, the sampling cylinder 1 is vertically lowered to the target layer depth in the borehole, and the sampling cylinder 1 is fixed stably; then the top plate 22 of the central shaft 23 is rotated to drive the bottom conical head 31 to rotate, so that the groove of the conical head 31 is aligned with the target sampling direction, the top plate 22 of the central shaft 23 is pressed downwards, and the conical head 31 is pushed vertically downwards. At this time, the arc-shaped head 326 in the corresponding direction of the groove is embedded in the groove, the spring 325 remains in a natural state, the gas sampling port 328 at the outer end of the gas sampling pipe 323 is communicated with the air inlet 4 of the sampling cylinder 1, and at the same time, the output port 327 of the sliding sleeve 324 is aligned with the gas guide pipe. The soil gas is pumped to the sampling bag by the air pump through the gas sampling pipe 323 and the gas guide pipe. The arc-shaped head 326 in the non-target direction slides along the inclined surface of the conical head 31, the spring 325 is compressed, the gas sampling pipe 323 retracts, and the arc-shaped baffle 321 closely adheres to the inner wall of the sampling cylinder 1 to block the air inlet 4 to prevent gas mixing. The air pump is started, and the soil gas in the target direction is continuously extracted through the gas guide pipe. After the sampling is completed, the air pump is turned off. The top plate 22 is loosened, the top spring 24 pushes the central shaft 23 and the conical head 31 to reset, the gas sampling pipe 323 returns to its initial position under the action of the spring 325, and the layer depth remains unchanged. The top plate of the central shaft is rotated 90°, so that the groove of the conical head 31 is aligned with the next target direction, and the above sampling process is repeated to ensure independent sampling of the samples in two directions. Finally, the double-direction sampling of all depths is completed layer by layer. The soil gas collected at different depths and different directions is numbered respectively to facilitate the analysis of the soil gas concentration at each position.

[0047] The oil pollution plume sampling device provided in this embodiment realizes the selective sampling of soil gas in different directions at the same layer depth by adjusting the direction of the conical head and the pressing linkage structure, avoiding gas mixing interference. Combined with the layer depth, azimuth numbering and three-dimensional coordinate recording, it provides high-resolution data support for the three-dimensional modeling of the pollution plume, solves the technical problem that traditional sampling equipment cannot separate gases in different directions, and provides a key tool for the accurate positioning of oil leakage pollution sources and the analysis of migration paths.

[0048] Example 3, on the basis of Examples 1 and 2, in order to weaken and even eliminate the interference of the residual gas in the gas guide pipe and the gas sampling cylinder on the soil gas sample as much as possible, this embodiment proposes an optimized method combining inert gas replacement and segmented sampling. Before the sampling cylinder is lowered into the sampling point borehole, the sampling cylinder cavity can be pre-filled with an inert gas, such as nitrogen. During the filling process, ensure that the pressure in the sampling cylinder is slightly higher than the atmospheric pressure to prevent external air from flowing back, and at the same time avoid damage to the sampling cylinder structure caused by excessive pressure. After the filling is completed, seal the filling interface to ensure that the inert gas in the sampling cylinder will not leak before sampling.

[0049] After lowering the sampling device filled with inert gas to a predetermined depth in the borehole, start the air pump to begin gas extraction. Since the sampling cylinder is initially filled with nitrogen, the inert gas is extracted first. This process continues until the gas components at the outlet end of the gas conduit are mainly nitrogen and there are no obvious characteristic components of soil gas. Then continue to extract gas until the sampling cylinder is correspondingly connected to the air inlet. At this time, the soil gas at this depth in the borehole is collected. During the collection process, continuously monitor the pressure, volume, and gas component changes of the gas in the sample collection bag to ensure that the soil gas is fully and stably collected. At the same time, record the time difference between the start time of collection and the time when the inert gas is completely discharged to provide reference data for subsequent judgment of the completion of collection. According to the preset collection time, the volume of the collected gas, or the change trend of the real-time monitored soil gas concentration, judge whether the collection of soil gas is completed. When the collection meets the expected requirements, stop the extraction of the air pump. After the positioning component resets, continue to extract until it is detected again that the gas components at the outlet end of the gas conduit are mainly nitrogen and there are no obvious characteristic components of soil gas, and then stop to complete the sampling of the soil gas at the target position. Repeat the above sampling process to ensure that pure soil gas is collected each time. In this way, the scientificity, reliability, and practicability of the oil pollution plume sampling device and method assisted by inert gas are ensured, effectively solving the problem that the residual gas in the gas conduit and the sampling cylinder affects the accuracy of the sample in the traditional sampling process, and improving the overall quality and efficiency of the oil pollution plume detection.

[0050] The above-described embodiments of the present invention do not constitute a limitation to the protection scope of the present invention. The basic concept of the present invention is to arrange radial survey lines centered on the pipe connection, combined with the layered directional sampling technology, to accurately collect soil gas samples at different depths and orientations, construct a three-dimensional pollution distribution model, and realize the three-dimensional characterization of the pollution plume and the precise positioning of the leakage source. The sampling device adopts a mechanical linkage design, supports multi-directional independent sampling at the same layer depth, avoids gas mixing interference, and significantly improves the detection accuracy and efficiency. Any modifications, equivalent replacements, and improvements made within the spirit and principles of the present invention shall be included within the protection scope of the claims of the present invention.

Claims

1. An oil pollution detection and monitoring method, characterized in that: It includes the following steps: Step 1: Determine the investigation area and mark the positions of the pipeline joints; Step 2: Layout survey lines within the investigation area, radiate outward from the center of the pipeline joint, arrange sampling points along the circumferential grid, and screen out the layout positions on both sides of the pipeline; Step 3: Drill to a set depth at the corresponding measurement points through a drilling device, ensuring that the drilling width is adapted to the sampling device; Step 4: Conduct a preliminary all-round collection of soil gas in the borehole and record the sampling results; Step 5: According to the preliminary sampling results, demarcate the measurement points with abnormal soil gas concentration and preliminarily determine the corresponding positions as suspected pollution points; Step 6: Conduct secondary sampling on the suspected pollution points, including separately collecting soil gas at each depth position towards and perpendicular to the center azimuth of the pipeline joint, and recording the results; After all the suspected pollution points are sampled according to the method described in this step, outline the three-dimensional soil gas pollution distribution based on the detection results of the soil gas concentration; Step 7: Based on the three-dimensional soil gas pollution distribution, conduct a single-hole concentration difference determination, predict the migration trend of pollutants according to the determination results, and determine the distribution range of the pollution plume; then compare the soil gas concentration results of adjacent suspected pollution points to determine the pollution source location.

2. The oil pollution detection and monitoring method according to claim 1, characterized in that: In Step 3, use a hollow auger drill to vertically drill to a predetermined depth, and immediately insert a PVC casing after drilling, and seal the bottom to prevent air from mixing in.

3. The oil pollution detection and monitoring method according to claim 1, characterized in that: In Step 5, before sampling, first select undisturbed points at the edge of the investigation as references, calculate the normal values of the pollutant background concentrations at each reference point, and then compare the concentration results obtained at each sampling point with the normal values of the reference point background concentrations. Areas exceeding 3 times the standard deviation of the background value or showing a gradient increase at multiple consecutive points are marked as suspected pollution points.

4. The oil pollution detection and monitoring method according to claim 1, characterized in that: In Step 6, gradually advance in the borehole of the suspected pollution point according to the preset depth levels, separately collect soil gas samples towards and perpendicular to the center azimuth of the pipeline joint, record the three-dimensional coordinates and environmental parameters, and analyze the pollutant concentrations in the samples; then based on the Kriging interpolation method, convert the discrete sampling point data into a continuous concentration field, generate four groups of independent three-dimensional pollution cloud maps, and synthesize a comprehensive three-dimensional concentration gradient tensor field through vector superposition.

5. The oil pollution detection and monitoring method according to claim 4, wherein: After sampling in the borehole at the suspected pollution point, the concentration difference judgment of a single borehole is carried out first. The judgment rule is: taking the pipeline flange connection as the coordinate origin, if the concentration on the east side is higher than that on the west side, it indicates that the pollutant migrates from east to west, and then combined with the groundwater flow direction data to verify whether the migration direction is consistent with the water flow direction; based on the concentration data of adjacent measuring points, the Kriging interpolation method is used to generate a horizontal concentration distribution map, and the concentration gradient change rate is calculated; when the gradient change rate > 15% / m, it is marked as the advancing direction of the pollution front to realize the judgment of the lateral expansion of the pollution plume; then, the concentration differences of different depth layers are compared. If the concentration of the shallow layer is higher than that of the deep layer, it indicates that the pollution source is close to the ground surface and there is a risk of shallow pipeline leakage; the spatial distances between the concentration peaks of all abnormal points and the flange nodes are statistically analyzed. If more than 80% of the peak points are distributed within the investigation area of the target flange point and the concentration decays with distance in line with the exponential model, then it is determined that the flange connection is the leakage source.

6. An oil pollution plume sampling device, which is applied to the secondary sampling in step 6 of the oil pollution plume detection method described in any one of claims 1-5, and is characterized in that: It includes a sampling cylinder, an adjusting component and a positioning component. The cylinder wall of the sampling cylinder is provided with an air inlet group at intervals along its length direction. Each air inlet group includes a plurality of air inlets communicated with the inner cavity of the sampling cylinder; the adjusting component includes a base plate, a central shaft and an adjusting seat. The central shaft is concentrically and slidably sleeved in the sampling cylinder. A base plate is slidably sleeved on the central shaft. The adjusting seat is rotatably sleeved on the central shaft. The bottom of the adjusting seat is fixed to the top surface of the base plate. A top spring is arranged between the top of the adjusting seat and the top plate at the top of the central shaft; the bottom of the central shaft extends below the base plate and is fixed with a tapered head, and grooves are symmetrically opened on the side walls on both sides of the tapered head; centered on the tapered head, the positioning component is arranged around it. The positioning component includes a positioning seat, a gas sampling pipe and an arc-shaped baffle. The positioning seat is fixed on the base plate. The gas sampling pipe is slidably installed on the positioning seat through a sliding sleeve. A ball seat is fixed at the inner end of the gas sampling pipe, and a spring is arranged between the ball seat and the positioning seat. An arc-shaped baffle is fixedly sleeved at the outer end of the gas sampling pipe; the gas sampling port at the end of the gas sampling pipe corresponds to the air inlet on the sampling cylinder, and the output port of the gas sampling pipe is communicated with a sample collection component on the ground through a gas guide pipe.

7. The oil pollution plume sampling device according to claim 6, characterized in that: The positioning seat is fixed on the base plate, and a sliding sleeve is fixedly sleeved on the positioning seat. The gas sampling pipe is slidably sleeved in the sliding sleeve, and a positioning hole is opened on the gas sampling pipe. An exhaust port is opened at a position corresponding to the positioning hole on the sliding sleeve, and a gas guide pipe is hermetically connected to the exhaust port.

8. The petroleum pollution plume sampling device according to claim 6, characterized in that: The sample collection component includes a gas guide pipe, an air pump and a sample collection bag. One end of the gas guide pipe is hermetically connected to the output port on the sliding sleeve, and a one-way valve is also arranged on the gas guide pipe. The other end of the gas guide pipe passes through the sampling cylinder and is communicated with the sample collection bag through the air pump to collect the soil gas collected.

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