Field sampling method for large areas and multiple points

Abstract

The present application relates to the technical field of gas sampling, in particular to a field sampling method for multi-point sampling in a large area in the wild, comprising the following steps: step 1, dividing the sampling area, and dividing the sampling area into a first area and a second area according to the distribution of roads in each sampling area, the first area is defined as within a predetermined distance from the road, and the second area is defined as outside the predetermined distance from the road. The field sampling method provided by the present application first classifies different sampling points in the wild, divides the sampling points into three types based on the distance from the road and whether it is a well gas sample, each type is sampled by a different container, and each type of gas sample is subjected to constant pressure and constant flow treatment before being input into a gas analysis system, so that the gas samples of various sampling points in the wild can be analyzed on site, restoring the current sampling point gas sample composition, especially suitable for multi-point sampling in a large area in the wild.

Description

Technical Field

[0001] This invention relates to the field of gas sampling technology, and more specifically to a field sampling method for large areas and multiple points in the field. Background Technology

[0002] Natural hydrogen can be produced through a variety of geological processes, including deep mantle dehydrogenation, magma-volcanic activity release, fault activity release, radiation-induced water splitting of radioactive minerals, water-rock reactions in iron-rich rocks, and high-temperature decomposition or microbial degradation of organic matter. Helium originates from two sources: mantle-derived and crustal-derived. Mantle-derived helium is primarily primordial helium captured during the early stages of Earth's formation, while crustal-derived helium is formed from the decay of uranium and thorium in rocks rich in radioactive minerals within the Earth's crust.

[0003] Because hydrogen and helium molecules are small, lightweight, and easily diffused, their formation conditions are demanding, significantly increasing the difficulty of exploration. However, the same easy diffusion of hydrogen and helium molecules makes soil gas detection an effective method for tracing localized enrichment of underground hydrogen and helium. Methane and carbon dioxide, as potential associated gases of hydrogen and helium, are also targets for soil gas detection; their content and isotopic characteristics help analyze the origin of hydrogen and helium.

[0004] It should be understood that in order to obtain a large amount of data over a wide area, large-scale sampling is required. Each area may employ a grid-based sampling system with a large number of sampling points. Currently, soil gas field sampling typically involves analyzing samples in a laboratory using gas detectors. However, because hydrogen and helium are highly volatile, after sequentially collecting samples from each sampling point using sampling bags or cylinders, the waiting time for collection and centralized transportation to the laboratory for measurement can lead to gas leakage and loss during long-term storage, resulting in inaccurate measurement results. Shortening the sampling time requires significant manpower (simultaneous sampling, collection, transportation, and testing at multiple points), material resources (sampling bags, cylinders, vehicles, etc.), and financial resources (long-term personnel costs, gas transportation costs, laboratory equipment usage costs, etc.). Therefore, it is impossible to send all samples to the laboratory during large-scale sampling. Summary of the Invention

[0005] To address the technical problems existing in large-area field gas sampling in the prior art, the first aspect of this invention proposes a field sampling method for large areas at multiple points, comprising the following steps:

[0006] Step 1: Divide the sampling area into a first area and a second area according to the distribution of roads in each sampling area. The first area is defined as within a predetermined distance from the road, and the second area is defined as outside the predetermined distance from the road. Within the sampling area, a sampling well is defined as a first sampling point, a sampling point in the second area is defined as a second sampling point, and a sampling point in the first area is defined as a third sampling point.

[0007] Step 2: Use different sampling containers to sample the gas at each sampling point. Specifically, use the first container for the first sampling point, the second container for the second sampling point, and the third container for the third sampling point.

[0008] Step 3: Pre-process the gas samples collected from each container, and perform on-site chromatography, mass spectrometry and carbon dioxide isotope analysis on the collected gas samples to obtain the concentrations of hydrogen and helium, as well as the concentration and carbon dioxide isotope ratio in the current gas sample.

[0009] Step 4: Flush the pretreatment and analysis pipelines with nitrogen gas to purge the pretreatment and analysis lines.

[0010] Step 5: Repeat steps 2 through 4 until all sampling points have been detected.

[0011] In step 3, the incoming gas sample is analyzed on-site by a gas analysis system. The pretreatment of the gas sample includes controlling the pressure and flow rate of the gas sample in the first container, the second container, and the third container, so that the gas sample in the first container, the second container, or the third container enters the gas analysis system at a predetermined pressure and flow rate.

[0012] Preferably, in step 1, the sampling area is divided into multiple sampling units according to the grid, and each sampling unit is sampled in a row-by-row or column-by-column order; in each sampling unit, the priority of each sampling point in the sampling unit is configured along the road extension direction.

[0013] Preferably, in step 2, within the same sampling unit, the third sampling point has a higher priority than the second sampling point, and the second sampling point has a higher priority than the first sampling point.

[0014] Preferably, in step 2, the first container includes a steel cylinder for storing a gas sample at a first pressure, the second container includes a flexible gas bag for storing a gas sample at a second pressure, the second pressure being less than the first pressure, and the third container includes an extraction pipe, the extraction pipe and the soil layer to be sampled forming a soil sample collection container.

[0015] Preferably, the capacity of the flexible air bag is 200-400ml, the flexible air bag includes an aluminum foil air bag, the length of the suction pipe is 15-25m, and the inner diameter of the suction pipe is 6mm.

[0016] Preferably, in step 3, the first container, the second container, and the third container enter the gas analysis system through different pretreatment pipelines. The first container enters the gas analysis system through a first injection path, the second container enters the gas analysis system through a second injection path, and the third container enters the gas analysis system through a third injection path.

[0017] Preferably, the first injection path includes a gas-liquid separator, a pressure stabilizing valve, and a flow regulating component; the second injection path includes a flow regulating valve, a suction device, a gas-liquid separator, a pressure stabilizing valve, and a flow regulating component; and the third injection path includes a suction device, a gas-liquid separator, a pressure stabilizing valve, and a flow regulating component. The first, second, and third injection paths include overlapping portions.

[0018] Preferably, the first injection path, the second injection path, and the third injection path constitute a pretreatment system. The pretreatment system and the gas analysis system are integrated into a mobile platform. The mobile platform includes a wheeled chassis, and the gas extraction device is detachably connected to the wheeled chassis. The total capacity of each injection path in the pretreatment system and the gas path in the gas analysis system is less than 30 ml.

[0019] Preferably, in step 4, after each gas detection, the pipes in the pretreatment system and the gas analysis system are emptied and filled with nitrogen.

[0020] Preferably, the gas analysis system includes a chromatography system, a mass spectrometry system, a spectral system, a data acquisition system, and a tail gas treatment system, wherein the mass spectrometry system is equipped with an independent turbomolecular pump and an electronic pressure controller;

[0021] The turbomolecular pump is used to vent the gas in the pipelines of the pretreatment system and the gas analysis system, and the electronic pressure controller is used to fill the pipelines of the gas analysis system and the pretreatment system with nitrogen.

[0022] Compared with the prior art, the advantages of the present invention are as follows:

[0023] The field sampling method proposed in this invention first classifies different sampling points in the field. Based on the distance from the road and whether it is a well gas sample, the sampling points are divided into three types. Each type is sampled using different containers. Before each type of gas sample is input into the gas analysis system, it undergoes constant pressure and constant flow processing, so that gas samples from various sampling points in the field can be analyzed on-site. This method of sampling gas samples from each sampling point on-site can ensure the validity of the analysis results and restore the composition of the gas sample at the current sampling point. It is especially suitable for multi-point sampling in large areas of the field. Attached Figure Description

[0024] The accompanying drawings are not intended to be drawn to scale. In the drawings, each identical or nearly identical component shown in the various figures may be denoted by the same reference numeral. For clarity, not every component is labeled in each figure. Embodiments of various aspects of the invention will now be described by way of example and with reference to the accompanying drawings, wherein:

[0025] Figure 1 This is a schematic diagram of the mobile gas collection system shown in this invention;

[0026] Figure 2 This is a schematic diagram of the structure of the mobile gas extraction system shown in this invention;

[0027] Figure 3 This is a schematic diagram of the sampling path of the first container shown in this invention;

[0028] Figure 4 This is a schematic diagram of the sampling path of the second container shown in this invention;

[0029] Figure 5 This is a schematic diagram of the sampling path of the third container shown in this invention;

[0030] Figure 6 This is a schematic diagram of the processing path for spectral analysis of gas samples as shown in this invention;

[0031] Figure 7 This is a schematic diagram of the pre-column separation process for gas samples as shown in this invention.

[0032] Figure 8 This is a schematic diagram of the processing path for mass spectrometry analysis of gas samples as shown in this invention. Detailed Implementation

[0033] To better understand the technical content of the present invention, specific embodiments are described below in conjunction with the accompanying drawings.

[0034] For soil gas collection, there may be different sampling scenarios, such as areas where equipment can or cannot be approached, or special oil and gas plant areas. For gases such as hydrogen and helium, which are extremely easy to dissipate, distributed sampling followed by centralized laboratory analysis and detection cannot accurately reflect the gas concentration. Therefore, it is essential to achieve real-time on-site sampling and analysis.

[0035] The first aspect of this invention proposes a field sampling method for large areas and multiple points, based on a mobile gas sampling system, combined with... Figure 1 and Figure 2 As shown, the mobile gas sampling system includes a gas sampling container 10, a pretreatment system 20, and a gas analysis system 30. The gas sampling container 10 includes any one or more of a first container 11, a second container 12, and a third container 13. The sampling method includes the following steps:

[0036] ① Division of sampling area and sampling points

[0037] Step 1: Divide the sampling area into a first area and a second area based on the distribution of roads within each sampling area. The first area is defined as within a predetermined distance from the road, and the second area is defined as outside the predetermined distance from the road. Within the sampling area, a sampling well is defined as the first sampling point, a sampling point in the second area is defined as the second sampling point, and a sampling point in the first area is defined as the third sampling point.

[0038] It should be understood that on-site sampling scenarios are generally divided into three categories. The first category is detection points that can be reached by mobile equipment. These detection points can be directly transported to the mass spectrometer on the mobile equipment through pipelines for detection. The second category is detection points that cannot be reached by mobile equipment. These detection points can be sampled using gas sampling bags and then detected by the mass spectrometer on the mobile equipment in a very short time. The third category is sampling wells in oil and gas plant areas. The gas pressure in the sampling wells is high, so steel cylinders can be used as sampling containers, and then detected by the mass spectrometer on the mobile equipment in a very short time.

[0039] Therefore, this application divides the sampling area into two regions based on the distance from the road, and further divides these two regions into two types of detection points: a second sampling point far from the road and a third sampling point close to the road. For special sampling wells, due to the high gas pressure inside the well, gas cylinder sampling can be performed directly as the first sampling point. In this way, all sampling points collected on-site can be divided into these three types of sampling points.

[0040] In an optional embodiment, the sampling area is divided into multiple sampling units according to a grid, and each sampling unit can be sampled in a row-by-row or column-by-column order; in each sampling unit, the priority of each sampling point in the sampling unit is configured along the road extension direction.

[0041] For example, multiple sampling units are numbered as (x1, y1), (x1, y2), (x2, y1), (x2, y2)...(xn, yn), and sampling is performed row by row according to (x1, y1), (x1, y2), (x1, y3)...(x1, yn). If in the current sampling unit, the road extends from the first point along the road direction to the nth point, then starting from the first point, the sampling points of the first region and the second region are sampled sequentially until all the sampling points in the sampling unit are completely sampled, and then the sampling of the next sampling unit begins.

[0042] ② Selection of sampling containers for different sampling points

[0043] Step 2: Use different sampling containers to sample the gas at each sampling point. Specifically, use the first container 11 for the first sampling point, the second container 12 for the second sampling point, and the third container 13 for the third sampling point.

[0044] It should be understood that the gas samples from each sampling point are different and have different characteristics. Therefore, different sampling containers can be used for sampling.

[0045] For the first sampling point, the gas sample pressure is high and can be sampled directly. Therefore, the first container 11 can be a steel cylinder. The steel cylinder is used to store the gas sample at the first pressure. The pressure of the gas sample inside the steel cylinder is usually 1 MPa to 4 MPa.

[0046] For the second sampling point, since it is far from the road and not convenient to extract directly through the pipeline, a gas sampling device is used to draw the gas sample into a flexible gas bag for collection. The flexible gas bag is used to store the gas sample at a second pressure, which is lower than the first pressure.

[0047] For the third sampling point, since it is close to the road, air can be extracted directly using only a pipe. Therefore, the third container 13 includes an extraction pipe, and the extraction pipe and the soil layer to be sampled constitute a soil sample collection container.

[0048] In an optional embodiment, within the same sampling unit, the third sampling point has a higher priority than the second sampling point, and the second sampling point has a higher priority than the first sampling point.

[0049] Therefore, since air extraction is required when collecting data at the second sampling point, the air pump of the equipment needs to be disassembled. Thus, the third sampling point is sampled first using the pipeline, and then the second sampling point is sampled.

[0050] In a specific embodiment, for sampling at the first sampling point, the first container 11 is connected to the sampling well, and the gas sample is forced into the first container 11 by the pressure of the sampling well; for sampling at the second sampling point, a gas channel of a predetermined size is drilled at the sampling point using a drilling tool, a probe is placed in the gas channel, and an air extraction device 21 is connected between the gas channel and the second container 12 to extract the gas sample in the gas channel into the second container 12; for sampling at the third sampling point, a gas channel of a predetermined size (approximately 2 cm in diameter and approximately 1 m in length) is drilled at the sampling point using a drilling tool, a probe is placed in the gas channel, and the two ends of the third container 13 are connected to the gas channel and the pretreatment system 20, respectively.

[0051] ③ Gas sample pretreatment and analysis

[0052] Step 3: Pre-process the gas samples collected from each container, and perform on-site chromatography, mass spectrometry, and carbon dioxide isotope analysis on the collected gas samples to obtain the concentrations of hydrogen and helium, as well as the concentration and carbon dioxide isotope ratio in the current gas sample.

[0053] Because the gas content, pressure, and uniformity of the first container 11, the second container 12, and the third container 13 are different, the gas samples of each container need to be processed differently.

[0054] The gas analysis system 30 performs on-site analysis of the incoming gas sample. The pretreatment of the gas sample includes controlling the pressure and flow rate of the gas sample in the first container 11, the second container 12, and the third container 13, so that the gas sample in the first container 11, the second container 12, or the third container 13 enters the gas analysis system 30 at a predetermined pressure and flow rate.

[0055] This ensures that all gas samples enter the gas analysis system 30 at the same pressure and speed, which helps maintain the consistency of the test results and more accurately reflects the analysis results of gas samples at each sampling point.

[0056] Furthermore, the first container 11, the second container 12, and the third container 13 enter the gas analysis system 30 through different pretreatment pipelines. The first container enters the gas analysis system 30 through the first injection path, the second container enters the gas analysis system 30 through the second injection path, and the third container enters the gas analysis system 30 through the third injection path.

[0057] The pretreatment system 20 consists of a first injection path, a second injection path, and a third injection path.

[0058] Since gases are compressible, the pressure and flow rate of the sample gas must be maintained to ensure a stable amount of sample gas entering the system each time. Therefore, the gas samples in the first container 11, the second container 12, or the third container 13 are all subject to pressure and flow stabilization control to ensure the flow rate of the sample gas.

[0059] In an optional embodiment, the gas pressure output by the pretreatment system 20 to the gas analysis system 30 is 0.1 MPa.

[0060] To ensure that each gas sample enters the gas analysis system 30 at the same pressure and flow rate, different processing is required for the gas samples at the three sampling points. For example, the gas sample at the first sampling point is a high-pressure gas sample, so the gas sample pressure and flow rate need to be reduced; the gas sample at the second sampling point is a low-pressure gas sample, so the gas sample needs to be pressurized and the flow rate controlled; and the gas sample at the third sampling point is a low-pressure gas sample, and the gas sample is not uniform, so the gas sample needs to be pressurized and the flow rate controlled during pretreatment.

[0061] It should be understood that during the sampling process of the third container, due to the long length of the pipeline, the gas sample enters the mass spectrometry system unevenly when it is drawn in. Therefore, the concentration of the gas sample at different detection times should be taken into account during detection.

[0062] Specifically, let V be the volume of the pipe and V be the volume of the underground borehole. 管 (V 管 V can be calculated using the pipe diameter R and the drilling depth h, i.e. 管 =1 / 4πR 2 *h), the pumping rate of the pumping device is Q, in ml / min. The delay time T from the sample gas to the detector is calculated based on the pumping rate Q and the volume V of the pipeline, in seconds. After unit alignment, the calculation is performed: T = V / Q, that is, from the start of pumping, after a delay of T seconds, detection begins. For any time tx after the start of detection, the concentration C of hydrogen or helium is... h2 x or C He x can be expressed by the following formula:

[0063]

[0064] Where t0 is the time of the first peak, t N For the time of the last peak, C t Let C be the concentration of hydrogen or helium at time t. h2 x or C He x, with a test interval of 1 minute per test.

[0065] Therefore, the above formula can be used to obtain the concentration corresponding to each detection data, that is, the correspondence between the concentration and quantity of hydrogen or helium.

[0066] Thus, the detection results at different times correspond to the detection results at different concentrations. Among them, the concentration peak is closer to the original concentration of hydrogen and helium in the gas sample.

[0067] In a specific embodiment, the first injection path includes a gas-liquid separator 27, a pressure regulating valve 22, and a flow regulating component 23; the second injection path includes a flow regulating valve 121, a vacuum device 21, a gas-liquid separator 27, a pressure regulating valve 22, and a flow regulating component 23; and the third injection path includes a vacuum device 21, a gas-liquid separator 27, a pressure regulating valve 22, and a flow regulating component 23. The first, second, and third injection paths include overlapping portions.

[0068] Since the flexible air bag has a small air volume, in order to ensure that the air volume entering the gas analysis system 30 after being pressurized by the air extraction device 21 is uniform, in an optional embodiment, the input end of the air extraction device 21 is provided with a first gas selector 24. The first gas selector 24 is provided with a first input port and a second input port. The first input port is connected to the second container 12 through the flow regulating valve 121, and the second input port is connected to the third container 13.

[0069] Thus, the flow regulating valve 121 set at the first input port of the first gas selector 24 can control the amount of air entering the suction device 21 from the flexible air bag, ensuring that the input and output flow rates are preset values ​​when the output pressure is at a preset value. Since the inner diameter and length of the suction pipe are fixed values, which constrain the maximum value of the intake air volume, it is not necessary to set a flow regulating valve in the suction pipe.

[0070] In an optional embodiment, the output end of the vacuum device 21 is provided with a second gas selector 25. The second selector has a third input port and a fourth input port, and the third input port of the second selector is connected to the output end of the vacuum device 21. The output end of the second selector is provided with a gas-liquid separator 27, and the output end of the gas-liquid separator 27 is provided with a third gas selector 26, which is located at the input end of the pressure regulating valve 22.

[0071] Thus, since water is easily liquefied after the gas sample is pressurized by the gas extraction device 21, by setting up the gas-liquid separation tank 27, the gas sample can be separated into gas and liquid after passing through the gas-liquid separation tank 27. The gas sample after gas-liquid separation is conducive to obtaining better test results.

[0072] In specific embodiments, such as Figure 3As shown, taking the injection of a gas cylinder as an example, the gas cylinder is connected to the fourth input port of the second gas selector 25. The gas in the gas cylinder enters the second gas selector 25 through the first injection path, and then enters the gas-liquid separator 27. After passing through the gas-liquid separator 27, gas-liquid separation is achieved, and then the gas enters the third gas selector 26. After passing through the pressure regulating valve 22 and the flow regulating component 23, the gas flow entering the ten-way injection valve 31 is a constant pressure and constant flow gas sample.

[0073] In specific embodiments, such as Figure 4 As shown, taking a flexible gas bag as an example, the flexible gas bag is connected to the flow regulating valve 121. Through the pressurization action of the suction device 21, the gas sample in the flexible gas bag passes through the flow regulating valve 121, the first gas selector 24 and the suction device 21 in sequence. After being pressurized by the suction device 21, it enters the second gas selector 25 and the gas-liquid separator 27. After passing through the gas-liquid separator 27, gas-liquid separation is achieved, and then it enters the third gas selector 26. Finally, through the pressure regulating valve 22 and the flow regulating component 23, the gas flow entering the ten-way sample inlet valve 31 is a constant pressure and constant flow gas sample.

[0074] Optionally, the suction device 21 is detachably connected to the movable platform. When sampling with a flexible air bag, the suction device 21 can be detached and transferred to the sampling point by the sampling personnel. At the sampling point, a drilling tool (probing metal tube) is used to drill an air channel of a predetermined size, the probing tool is placed in the air channel, and the suction device 21 is connected between the air channel and the flexible air bag to draw the air sample from the air channel into the flexible air bag.

[0075] In specific embodiments, such as Figure 5 As shown, taking the gas extraction pipeline as an example, the two ends of the gas extraction pipeline are connected to the gas channel and the first gas selector 24, respectively. Through the gas extraction action of the gas extraction device 21, the gas sample in the gas channel enters the first gas selector 24 and the gas extraction device 21 through the gas extraction pipeline. After being pressurized by the gas extraction device 21, it enters the second gas selector 25 and the gas-liquid separator 27. After passing through the gas-liquid separator 27, gas-liquid separation is achieved, and then it enters the third gas selector 26. Finally, through the pressure stabilizing valve 22 and the flow regulating component 23, the gas flow entering the ten-way injection valve 31 is made into a constant pressure and constant flow gas sample.

[0076] It should be understood that, since the first container 11, the second container 12, or the third container 13 needs to be frequently disassembled from the pipeline during sampling and testing, it is preferable that the first container 11, the second container 12, or the third container 13 be detachably connected to the sample inlet path of the pretreatment system. For example, quick-release connectors can be used.

[0077] The pretreatment system 20 and the gas analysis system 30 are integrated into a mobile platform, which includes a wheeled chassis, such as a manned or unmanned wheeled chassis, that can travel on flat roads to facilitate transfer to the target sampling point or a location close to the sampling point.

[0078] Optionally, the air extraction device 21 is detachably connected to the wheeled chassis.

[0079] In the above embodiments, in order to avoid the residual gas in the fixed pipes of the device from affecting the gas sample, the gas path capacity between each sample inlet path in the pretreatment system 20 and the gas analysis system 30 is A, and the smallest capacity among the first container 11, the second container 12 or the third container 13 is B, wherein B≥10A.

[0080] Optionally, the capacity of the flexible gas bag is 200-400ml, the flexible gas bag includes an aluminum foil gas bag, the length of the gas extraction pipe is 15-25m, the inner diameter of the gas extraction pipe is 6mm, and the gas path capacity between each sample injection path in the pretreatment system 20 and the gas analysis system 30 is less than 30ml.

[0081] Thus, during detection, the upstream gas is discarded and not detected, that is, the gas path between each sample introduction path in the pretreatment system 20 and the gas analysis system 30 is emptied.

[0082] ④ Flushing of pretreatment and analysis pipelines

[0083] Step 4: Flush the pretreatment and analysis pipelines with nitrogen gas to purge them.

[0084] After each gas detection, the pipes in the pretreatment system 20 and the gas analysis system 30 are emptied and filled with nitrogen.

[0085] This avoids the possibility that residual gas samples in the pipeline will interfere with the next gas sample analysis.

[0086] Optionally, the gas analysis system 30 includes a chromatography system, a mass spectrometry system, a spectral system, a data acquisition system, and an exhaust gas treatment system. The mass spectrometry system is equipped with an independent turbomolecular pump and an electronic pressure controller.

[0087] The turbomolecular pump is used to vent the gas in the pipelines of the pretreatment system 20 and the gas analysis system 30, and the electronic pressure controller is used to fill the pipelines of the gas analysis system 30 and the pretreatment system 20 with nitrogen.

[0088] Optionally, the electronic pressure controller includes a nitrogen gas source with multiple outputs, one of which can be connected to the gas inlet of the pretreatment system 20 (the gas inlet of the first, second, and third sample inlet paths) for flushing the pipelines in the pretreatment system 20 and the gas analysis system 30. The turbomolecular pump can simultaneously perform suction to extract the residual exhaust gas from the pipelines and use nitrogen to flush the pipelines to avoid residual gas samples affecting the next gas sample.

[0089] 4-1 Gas Sample Analysis Process of Gas Analysis System

[0090] like Figure 6 As shown, after the gas has undergone pressure and flow stabilization, it enters the ten-way injection valve 31 for the detection of hydrogen and helium concentrations and carbon dioxide concentrations and their isotopes. The gas path for detecting hydrogen and helium concentrations is shown by the red line in the figure, and the gas path for detecting carbon dioxide concentrations and their isotopes is shown by the blue line.

[0091] Specifically, the gases used for hydrogen and helium concentration detection enter the chromatographic system through the ten-way injection valve 31 via the cut valve for pre-separation. First, air and the sample that will elute later are directly discharged from the system in the pre-column 33. Then, the sample processed by the pre-column 33 mainly contains hydrogen, helium and a small amount of air. At this point, it enters the first separation column 36 for further separation. After the hydrogen and helium enter the second separation column 37, the remaining air is discharged from the system.

[0092] After hydrogen and helium are separated from the second separation column 37, they enter the mass spectrometry system and are separated using a quadrupole. The mass number data with M / Z=2 and M / Z=4 are output respectively, thereby obtaining the concentrations of hydrogen and helium.

[0093] Specifically, the device used to measure carbon dioxide concentration and isotopes has a measurement range of only 300ppm to 2000ppm. On the one hand, its measurement range is relatively small. Therefore, a dilution module is added to the system. By fixing the flow rate of the sample gas, such as 50sccm, zero-level air 38 is added at the end for dilution, thereby widening the measurement range and ensuring that the instrument can measure 300ppm to 20000ppm.

[0094] Specifically, such as Figure 6 As shown, taking a gas sample from a steel cylinder as an example, the gas sample enters the gas-liquid separator 27 through the second gas selector 25 and then enters the inlet. After exiting the inlet, it enters the third gas selector 26 and then enters the pressure regulating valve 22 → flow regulating component 23 → port 9 of the ten-way injection valve 31 → quantitative loop 32 → port 1 → port 0 and exits into the dilution and mixing chamber 35 of the carbon dioxide concentration and isotope detector → spectral analysis (shown by the blue line).

[0095] like Figure 7 As shown, the ten-way injection valve 31 is opened, and the nitrogen gas in the electronic pressure controller 39 enters the ten-way injection valve 31 through port 7 → port 8 → quantitative loop 32 (carrying the gas in the quantitative loop of the previous step) → port 1 → port 2 → pre-column 33 → port 6 → port 5 → first separation column 36 → port 5 of the six-way switching valve 34 → port 4 → second separation column 37 → mass spectrometry analysis (shown by the red line).

[0096] The main function of this step is to carry the sample in the quantitative loop 32 into the mass spectrometer separation system for separation in the pre-column 33. Since the velocity of helium and hydrogen is greater than that of other components such as air, the ten-way injection valve 31 is immediately closed after all the helium and hydrogen have come out of the pre-column 33 and entered the first separation column 36.

[0097] like Figure 8 As shown, after the separation in pre-column 33 is completed, hydrogen, helium, and a small amount of oxygen and nitrogen enter the first separation column 36. Nitrogen gas, output from the electronic pressure controller 39, flows from port 4 → port 5 → first separation column 36 → port 5 of the six-way switching valve 34 → port 4 → second separation column 37 → mass spectrometer. When hydrogen and helium have completely entered separation column 2 from separation column 1, oxygen and nitrogen remain in separation column 1. At this point, the six-way switching valve 34 opens, creating the following gas path.

[0098] In this state, the nitrogen gas from the electronic pressure controller 39 enters port 3 → port 4 of the six-way switching valve 34 → the second separation column 37 → mass spectrometer, completing the mass spectrometry detection of hydrogen and helium gas. Simultaneously, the oxygen and nitrogen gases in the first separation column 36 are carried by the nitrogen gas from the middle path of the electronic pressure controller 39 and continue to be vented through port 5 → port 6 of the six-way switching valve 34.

[0099] Step 5: Repeat steps 2 through 4 until all sampling points have been tested.

[0100] While the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the invention. Those skilled in the art can make various modifications and refinements without departing from the spirit and scope of the invention. Therefore, the scope of protection of the present invention shall be determined by the claims.

Claims

1. A field sampling method for large areas and multiple points in the field, characterized in that, Includes the following steps: Step 1: Divide the sampling area into a first area and a second area according to the distribution of roads in each sampling area. The first area is defined as within a predetermined distance from the road, and the second area is defined as outside the predetermined distance from the road. Within the sampling area, a sampling well is defined as a first sampling point, a sampling point in the second area is defined as a second sampling point, and a sampling point in the first area is defined as a third sampling point. Step 2: Use different sampling containers to sample the gas at each sampling point. For the first sampling point, use the first container (11) for sampling; for the second sampling point, use the second container (12) for sampling; and for the third sampling point, use the third container (13) for sampling. Step 3: Pre-process the gas samples collected from each container, and perform on-site chromatography, mass spectrometry and carbon dioxide isotope analysis on the collected gas samples to obtain the concentrations of hydrogen and helium, as well as the concentration and carbon dioxide isotope ratio in the current gas sample. Step 4: Flush the pretreatment and analysis pipelines with nitrogen to purge any residual gas samples from the pretreatment and analysis pipelines. Step 5: Repeat steps 2 through 4 until all sampling points have been detected. In step 3, the gas sample is analyzed on-site by the gas analysis system (30). The pretreatment of the gas sample includes controlling the pressure and flow rate of the gas sample in the first container, the second container and the third container, so that the gas sample in the first container (11), the second container (12) or the third container (13) enters the gas analysis system (30) at a predetermined pressure and flow rate.

2. The field sampling method for large areas and multiple points in the field according to claim 1, characterized in that, In step 1, the sampling area is divided into multiple sampling units according to the grid, and each sampling unit is sampled in a row-by-row or column-by-column order; in each sampling unit, the priority of each sampling point in the sampling unit is configured along the road extension direction.

3. The field sampling method for large areas and multiple points in the field according to claim 2, characterized in that, In step 2, within the same sampling unit, the third sampling point has a higher priority than the second sampling point, and the second sampling point has a higher priority than the first sampling point.

4. The field sampling method for large areas and multiple points in the field according to claim 1, characterized in that, In step 2, the first container (11) includes a steel cylinder for storing a gas sample at a first pressure, the second container (12) includes a flexible air bag for storing a gas sample at a second pressure, the second pressure being less than the first pressure, and the third container (13) includes an extraction pipe, the extraction pipe and the soil layer to be sampled forming a soil sample collection container.

5. The field sampling method for large areas and multiple points in the field according to claim 4, characterized in that, The flexible air bag has a capacity of 200-400ml, the flexible air bag includes an aluminum foil air bag, the length of the suction pipe is 15-25m, and the inner diameter of the suction pipe is 6mm.

6. The field sampling method for large areas and multiple points in the field according to claim 1, characterized in that, In step 3, the first container (11), the second container (12), and the third container (13) enter the gas analysis system (30) through different pretreatment pipelines. The first container enters the gas analysis system (30) through the first injection path, the second container enters the gas analysis system (30) through the second injection path, and the third container enters the gas analysis system (30) through the third injection path.

7. The field sampling method for large areas and multiple points in the field according to claim 6, characterized in that, The first injection path includes a gas-liquid separator (27), a pressure regulating valve (22), and a flow regulating component (23). The second injection path includes a flow regulating valve (121), a suction device (21), a gas-liquid separator (27), a pressure regulating valve (22), and a flow regulating component (23). The third injection path includes a suction device (21), a gas-liquid separator (27), a pressure regulating valve (22), and a flow regulating component (23). The first, second, and third injection paths include overlapping portions.

8. The field sampling method for large areas and multiple points according to claim 6 or 7, characterized in that, The first injection path, the second injection path and the third injection path constitute a pretreatment system (20). The pretreatment system (20) and the gas analysis system (30) are integrated into a mobile platform. The mobile platform includes a wheeled chassis and a gas extraction device (21) is detachably connected to the wheeled chassis. The total capacity of each injection path in the pretreatment system (20) and the gas path in the gas analysis system (30) is less than 30 ml.

9. The field sampling method for large areas and multiple points in the field according to claim 8, characterized in that, In step 4, after each gas detection, the pipes in the pretreatment system (20) and the gas analysis system (30) are emptied and filled with nitrogen.

10. The field sampling method for large areas and multiple points according to claim 9, characterized in that, The gas analysis system (30) includes a chromatography system, a mass spectrometry system, a spectral system, a data acquisition system, and a tail gas treatment system. The mass spectrometry system is equipped with an independent turbomolecular pump and an electronic pressure controller. The turbomolecular pump is used to vent the gas in the pipelines of the pretreatment system (20) and the gas analysis system (30), and the electronic pressure controller is used to fill the pipelines of the gas analysis system (30) and the pretreatment system (20) with nitrogen.

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