Field large-area multi-point field sampling method

Abstract

The invention relates to the technical field of gas sampling, in particular to a field large-area multi-point field sampling method, which comprises the following steps of: 1, segmenting a sampling area, dividing the sampling area into a first area and a second area according to the distribution of roads in each sampling area, defining the first area to be within a preset distance from the roads, and defining the second area to be within a preset distance from the roads; the second region is defined outside a predetermined distance from the road. According to the on-site sampling method, firstly, different sampling points in the field are classified, the sampling points are divided into three types based on the distance from a road and whether the sampling points are well gas samples or not, gas sample sampling is carried out on each type through different containers, constant-pressure and constant-flow treatment is carried out on each type of gas samples before the gas samples are input into a gas analysis system, and the gas samples are subjected to gas sampling; the gas samples of various sampling points in the field can be analyzed on site, the components of the gas samples of the current sampling points are reduced, and the device is particularly suitable for multi-point sampling in large areas in the field.

Description

Technical Field

[0001] The invention relates to the technical field of gas sampling, and in particular to a field sampling method for multiple points in a large outdoor area. Background Art

[0002] Natural hydrogen can be produced from a variety of geological processes, including deep mantle dehydrogenation, magma-volcanic activity gas release, fault activity gas release, radioactive mineral water decomposition, iron-rich rock water-rock reaction, high-temperature cracking of organic matter or microbial degradation, etc. The origin of helium is divided into mantle source and crust source. Mantle source helium is mainly the original helium captured in the early process of the formation of the earth, and crust source helium is the helium formed by the decay of rock uranium and thorium elements rich in radioactive minerals in the crust.

[0003] Since hydrogen and helium molecules are small, light, and easy to diffuse, the reservoir formation conditions are harsh, which greatly increases the difficulty of exploration. However, due to the easy diffusion of hydrogen and helium molecules, soil gas detection has become an effective method to trace the local enrichment of underground hydrogen and helium. Gases such as methane and carbon dioxide in soil gas are possible co-existing gases of hydrogen and helium. Their content and isotopic characteristics are helpful for analyzing the origin of hydrogen and helium, and are also the objects of soil gas detection.

[0004] It should be understood that in order to obtain a large amount of surface data, large-scale sampling will be carried out in large areas. Grid points can be used in each area, and the number of sampling points is large. At present, field sampling of soil gas is usually analyzed in the laboratory using a gas detector after sampling. However, since hydrogen and helium are very easy to lose, after collecting each sampling point in sequence through sampling bags or cylinders, waiting for the collection to be completed and transported to the laboratory for measurement will cause leakage loss of gas after long-term storage, resulting in inaccurate measurement results. Shortening the sampling time requires a lot of manpower (multi-point simultaneous sampling, collection, transportation, and testing), material resources (sampling bags, cylinders, vehicles, etc.), and financial resources (long-term labor costs, transportation costs, laboratory instrument usage costs, etc.). Therefore, it is impossible to send all samples to the laboratory when sampling in a large area. Summary of the invention

[0005] In view of the technical problems existing in the prior art of field large-area gas sampling, the first aspect of the present invention provides a field large-area multi-point sampling method, comprising the following steps:

[0006] Step 1, segmenting 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. In the sampling area, the sampling well is defined as a first sampling point, the sampling point in the second area is defined as a second sampling point, and the sampling point in the first area is defined as a third sampling point;

[0007] Step 2: Use different sampling containers for each sampling point to sample the gas, wherein a first container is used for sampling at the first sampling point, a second container is used for sampling at the second sampling point, and a third container is used for sampling at the third sampling point;

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

[0009] Step 4: flush the pre-treatment and analysis pipelines with nitrogen to exhaust the pre-treatment and analysis;

[0010] Step 5: Repeat steps 2 to 4 until all sampling points are tested.

[0011] Among them, in step 3, the connected gas sample is analyzed on-site by the gas analysis system, and the pre-processing of the gas sample includes controlling the pressure and flow rate of the gas samples in the first container, the second container and the third container, so that the gas samples in the first container, the second container or the third container enter the gas analysis system at a predetermined pressure and flow rate.

[0012] Preferably, in step 1, the sampling area is divided into a plurality of sampling units according to a 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 extension direction of the road.

[0013] Preferably, in step 2, in the same sampling unit, the priority of the third sampling point is higher than that of the second sampling point, and the priority of the second sampling point is higher than that of the first sampling point.

[0014] Preferably, in step 2, the first container includes a steel cylinder, which is used to store gas samples at a first pressure; the second container includes a flexible air bag, which is used to store gas samples at a second pressure, wherein the second pressure is less than the first pressure; and the third container includes an exhaust pipe, which together with the soil layer to be sampled constitutes a soil sample collection container.

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

[0016] Preferably, in step 3, the first container, the second container and the third container enter the gas analysis system through different pretreatment pipelines respectively, 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 separation tank, a pressure-stabilizing valve and a flow regulating component, the second injection path includes a flow regulating valve, a vacuum device, a gas-liquid separation tank, a pressure-stabilizing valve and a flow regulating component, the third injection path includes a vacuum device, a gas-liquid separation tank, a pressure-stabilizing valve and a flow regulating component, and the first injection path, the second injection path and the third injection path include overlapping parts.

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

[0019] Preferably, in step 4, after each gas detection, the pipelines in the pre-treatment system and the gas analysis system are evacuated 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 an exhaust gas treatment system, and the mass spectrometry system is equipped with an independent turbomolecular pump and an electronic pressure controller;

[0021] The turbomolecular pump is used to evacuate the gas in the pipelines of the pre-treatment system and the gas analysis system, and the electronic pressure controller is used to fill nitrogen into the pipelines of the gas analysis system and the pre-treatment system.

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

[0023] The field sampling method proposed in the present invention first classifies different sampling points in the field, and divides the sampling points into three types based on the distance from the road and whether they are well gas samples. Each type of gas sample is sampled through a different container, and each gas sample is subjected to constant pressure and constant current processing before being input into the gas analysis system, so that the gas samples of various sampling points in the field can be analyzed on-site. Through this on-site collection and on-site analysis of the gas samples of each sampling point one by one, the validity of the analysis results can be guaranteed, and the gas sample composition of the current sampling point can be restored. It is particularly suitable for multi-point sampling in large areas in the field. BRIEF DESCRIPTION OF THE DRAWINGS

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

[0025] Figure 1 It is a principle block diagram of the cruise gas collection system shown in the present invention;

[0026] Figure 2 It is a structural schematic diagram of the cruise gas production system shown in the present invention;

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

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

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

[0030] Figure 6 is a schematic diagram of a processing path for spectral analysis of a gas sample shown in the present invention;

[0031] Figure 7 It is a schematic diagram of a processing path for pre-column separation of a gas sample shown in the present invention;

[0032] Figure 8 It is a schematic diagram of the processing path for mass spectrometry analysis of gas samples shown in the present invention. DETAILED DESCRIPTION

[0033] In order to better understand the technical content of the present invention, specific embodiments are given and described as follows in conjunction with the accompanying drawings.

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

[0035] The first aspect of the present invention proposes a field sampling method for multiple points in a large area, based on a cruise gas sampling system, combined with Figure 1 and Figure 2 As shown, the cruise gas sampling system includes a gas sampling container 10, a pre-treatment system 20 and a gas analysis system 30, wherein 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 areas and sampling points

[0037] Step 1: Segment the sampling area, and 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, the sampling well is defined as the first sampling point, the sampling point within the second area is defined as the second sampling point, and the sampling point within 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 the detection points that can be reached by mobile devices. These detection points can be directly transported to the mass spectrometer on the mobile device through pipelines for detection. The second category is the detection points that cannot be reached by mobile devices. These detection points can be sampled using gas sample bags and then detected using the mass spectrometer on the mobile device in a very short time. The third category is the sampling wells in the oil and gas plant area. The gas pressure in the sampling wells is high, and steel cylinders can be used as sampling containers, and then detected using the mass spectrometer on the mobile device in a very short time.

[0039] Therefore, this application divides the sampling area into two areas according to the characteristics of the distance from the road in the sampling area, and divides the detection points into two categories according to the two areas, namely, the second sampling point far away from the road and the third sampling point close to the road. For special sampling wells, due to the high gas pressure in the wells, cylinder sampling can be directly used as the first sampling point. In this way, all sampling points collected on site can be divided into these three categories 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 extension direction of the road.

[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 area and the second area are sampled in turn until the sampling points in the sampling unit are completely sampled, and then sampling of the next sampling unit is started.

[0042] ②Choice of sampling containers at different sampling points

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

[0044] It should be understood that the gas sample at each sampling point is different and has different characteristics, so 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, so optionally, the first container 11 can be a steel cylinder, which is used to store the gas sample at the first pressure. The pressure of the gas sample inside the steel cylinder is usually 1MP to 4MP.

[0046] For the second sampling point, since it is far away from the road and not conducive to direct extraction through the pipeline, a vacuum device is used to draw the gas sample into a flexible air bag for collection. The flexible air 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 directly pumped through a pipeline. Therefore, the third container 13 includes an air pumping pipeline, and the air pumping pipeline and the soil layer to be sampled constitute a soil sample collection container.

[0048] In an optional embodiment, in 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] In this way, since air needs to be pumped out when collecting at the second sampling point, the vacuum pump of the equipment needs to be disassembled. Therefore, the third sampling point is sampled using a pipeline first, 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 pressed into the first container 11 by the pressure of the sampling well; for sampling at the second sampling point, an airway of a predetermined size is drilled out at the sampling point using a drilling tool, a detection tool is placed in the airway, and a vacuum device 21 is connected between the airway and the second container 12 to draw the gas sample in the airway into the second container 12; for sampling at the third sampling point, an airway of a predetermined size (about 2 cm in diameter and about 1 m in length) is drilled out at the sampling point using a drilling tool, the detection tool is placed in the airway, and the two ends of the third container 13 are respectively connected to the airway and the pretreatment system 20.

[0051] ③ Gas sample pretreatment and analysis

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

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

[0054] Among them, the connected gas sample is analyzed on-site through the gas analysis system 30, and the pre-processing 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] In this way, it can be ensured that various gas samples enter the gas analysis system 30 at the same pressure and speed, which is conducive to maintaining the uniformity of the detection results and more accurately reflecting the analysis results of the 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 respectively. 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 pre-treatment system 20 is composed of the first injection path, the second injection path and the third injection path.

[0058] Since gas is compressible, the pressure and flow rate of the sample gas must be guaranteed to ensure that the amount of sample gas entering the system is stable each time. Therefore, the gas samples in the first container 11, the second container 12 or the third container 13 are all controlled to stabilize the pressure and flow to ensure the flow rate of the sample gas.

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

[0060] In order to ensure that each gas sample enters the gas analysis system 30 at the same pressure and flow rate, the gas samples at the three sampling points need to be processed differently. For example, the gas sample at the first sampling point is a high-pressure gas sample, and 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, and the gas sample needs to be pressurized and the flow rate needs to be controlled. The gas sample at the third sampling point is a low-pressure gas sample, and the gas sample is uneven, so it needs to be pressurized and the flow rate needs to be controlled during pre-treatment.

[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. Therefore, the concentration of the gas sample at different detection times should be considered during detection.

[0062] Specifically, define the volume of the pipeline as V and the volume of the underground hole as V 管 (V 管 It can be calculated using the pipe diameter R and the hole depth h, that is, V 管 =1 / 4πR 2 *h), the pumping rate of the pumping device is Q, the unit is ml / min, the delay time T from the sample gas to the detector is calculated according to the pumping rate Q and the volume V of the pipeline, the unit is s, and the calculation is T=V / Q after the units are aligned, that is, from the moment of starting pumping, after a delay of Ts, the detection begins. For any time tx after the start of detection, the concentration C of hydrogen or helium 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 is the time of the last peak, C t is the concentration of hydrogen or helium at time t, C h2 x or C He x, the test interval is 1min / time.

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

[0066] In this way, the detection results at different times correspond to detection results of different concentrations, among which, when the concentration peak is the highest, it 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 separation tank 27, a pressure-stabilizing 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 separation tank 27, a pressure-stabilizing valve 22 and a flow regulating component 23, and the third injection path includes a vacuum device 21, a gas-liquid separation tank 27, a pressure-stabilizing valve 22 and a flow regulating component 23. The first injection path, the second injection path and the third injection path include overlapping parts.

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

[0069] In this way, the flow regulating valve 121 provided at the first input port of the first gas selector 24 can control the amount of gas entering the flexible gas bag into the air extraction device 21, and when the output pressure is ensured to be a preset value, the input and output flow rates are preset values. Since the inner diameter and length of the air extraction pipeline are fixed values, which constrain the maximum amount of air intake, there is no need to provide a flow regulating valve in the air extraction pipeline.

[0070] In an optional embodiment, the output end of the gas extraction device 21 is provided with a second gas selector 25, the second selector is provided with 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 gas extraction device 21. The output end of the second selector is provided with a gas-liquid separation tank 27, and the output end of the gas-liquid separation tank 27 is provided with a third gas selector 26, and the third gas selector 26 is located at the input end of the pressure regulating valve 22.

[0071] In this way, since water is easily liquefied after the gas sample is pressurized by the vacuum device 21, a gas-liquid separation tank 27 is provided to enable the gas sample to be separated into gas and liquid after passing through the gas-liquid separation tank 27. Gas sampling after gas-liquid separation is conducive to obtaining better test results.

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

[0073] In a specific embodiment, Figure 4 As shown, taking the flexible air bag as an example, the flexible air bag is connected to the flow regulating valve 121. Through the pressurizing action of the vacuum device 21, the gas sample in the flexible air bag passes through the flow regulating valve 121, the first gas selector 24 and the vacuum device 21 in sequence. After being pressurized by the vacuum device 21, the gas sample enters the second gas selector 25 and the gas-liquid separation tank 27. After passing through the gas-liquid separation tank 27, the gas-liquid separation is achieved, and then the gas sample enters the third gas selector 26. After that, the gas sample passes through the pressure stabilizing valve 22 and the flow regulating component 23, so that the gas flow entering the ten-way injection 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 the flexible air bag, the suction device 21 can be detached and transferred to the sampling point by the sampling personnel, and an air passage of a predetermined size is drilled at the sampling point using a drilling tool (detection metal tube), the detection tool is placed in the air passage, the suction device 21 is connected between the air passage and the flexible air bag, and the gas sample in the air passage is sucked into the flexible air bag.

[0075] In a specific embodiment, Figure 5 As shown, taking the exhaust pipeline as an example, the two ends of the exhaust pipeline are respectively connected to the airway and the first gas selector 24. Through the exhaust action of the exhaust device 21, the gas sample in the airway enters the first gas selector 24 and the exhaust device 21 through the exhaust pipeline, and after being pressurized by the exhaust device 21, enters the second gas selector 25 and the gas-liquid separation tank 27, realizes gas-liquid separation after passing through the gas-liquid separation tank 27, and then enters the third gas selector 26, and then passes through the pressure regulating valve 22 and the flow regulating component 23, so that the airflow entering the ten-way injection valve 31 is 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 disconnected from the pipeline during the sampling and detection process, preferably, the first container 11, the second container 12 or the third container 13 is detachably connected to the injection path of the pretreatment system, for example, using a quick-release connector.

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

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

[0079] In the above embodiment, in order to prevent the residual gas in the fixed pipeline of the equipment from affecting the gas sample, the gas path capacity between each injection 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, where B≥10A.

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

[0081] In this way, during detection, the front-stage gas is discarded and not detected, that is, the gas path between each injection path in the pre-treatment system 20 and the gas analysis system 30 is emptied.

[0082] ④ Flushing of pre-treatment and analysis pipelines

[0083] Step 4: flush the pre-treatment and analysis pipelines with nitrogen to empty the pre-treatment and analysis pipelines;

[0084] After each gas detection, the pipelines in the pre-treatment system 20 and the gas analysis system 30 are evacuated and filled with nitrogen.

[0085] In this way, it can be avoided that the residual gas sample in the pipeline interferes 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, and the mass spectrometry system is equipped with an independent turbomolecular pump and an electronic pressure controller;

[0087] The turbomolecular pump is used to evacuate the gas in the pipelines of the pre-treatment system 20 and the gas analysis system 30 , and the electronic pressure controller is used to fill nitrogen into the pipelines of the gas analysis system 30 and the pre-treatment system 20 .

[0088] Optionally, the electronic pressure controller includes a nitrogen gas source, which includes multiple output ends, one of which can be connected to the air inlet end of the pretreatment system 20 (the air inlet ends of the first, second, and third injection paths), and is used to flush the pipes in the pretreatment system 20 and the gas analysis system 30. The turbomolecular pump can simultaneously perform suction to extract the remaining exhaust gas in the pipes, and flush the pipes with nitrogen to prevent the residual gas sample from 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 treated with pressure stabilization and flow stabilization enters the ten-way injection valve 31, the hydrogen and helium concentrations and the carbon dioxide concentration and its isotope are detected. The gas path for detecting the hydrogen and helium concentrations is shown by the red line in the figure, and the gas path for detecting the carbon dioxide concentration and its isotope is shown by the blue line in the figure.

[0091] Specifically, the gas used for hydrogen and helium concentration detection enters the chromatographic system through the cut valve from the ten-way injection valve 31 for pre-separation. First, the air and the sample that will peak 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 time, 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 spectrometer system and are separated by a quadrupole, outputting mass number data of M / Z=2 and M / Z=4 respectively, thereby obtaining the concentrations of hydrogen and helium.

[0093] Specifically, the device for measuring carbon dioxide concentration and isotopes has a measurement range of only 300ppm to 2000ppm. On the one hand, its measurement range is relatively small, so 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 back end for dilution, thereby widening the measurement range and ensuring that the instrument can measure 300ppm to 20000ppm.

[0094] Specifically, Figure 6 As shown, taking the gas sample of the cylinder as an example, the gas sample passes through the second gas selector 25, enters the gas-liquid separation tank 27, and enters the injection port. After exiting the injection port, 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 ring 32 → port 1 → port 0 and exits to the dilution 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 in the electronic pressure controller 39 enters port 7 of the ten-way injection valve 31 → port 8 → quantitative ring 32 (bringing the gas in the quantitative ring of the previous step backward) → 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 bring the sample in the quantitative ring 32 into the separation system of the mass spectrometer and separate it in the pre-column 33. Since the speed of helium and hydrogen is greater than that of other components such as air, when all the helium and hydrogen come out of the pre-column 33 and enter the first separation column 36, the ten-way injection valve 31 is immediately closed.

[0097] like Figure 8 As shown, after the separation of the pre-column 33 is completed, hydrogen, helium and a small amount of oxygen and nitrogen enter the first separation column 36, and the output nitrogen from the middle of the electronic pressure controller 39 is 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 completely enter the separation column 2 from the separation column 1, substances such as oxygen and nitrogen are still in the separation column 1. At this time, the six-way switching valve 34 is opened to become the following gas path.

[0098] In this state, the nitrogen on the right side of the electronic pressure controller 39 enters port 3 → port 4 of the six-way switching valve 34 → the second separation column 37 → mass spectrometry, completing the mass spectrometry detection of hydrogen and helium gases. At the same time, the oxygen, nitrogen and other gases in the first separation column 36 are carried by the nitrogen in the middle of the electronic pressure controller 39 and continue to be discharged from port 5 → port 6 of the six-way switching valve 34.

[0099] Step 5: Repeat steps 2 to 4 until all sampling points are tested.

[0100] Although the present invention has been disclosed as above with preferred embodiments, it is not intended to limit the present invention. A person with ordinary knowledge in the technical field to which the present invention belongs may make various changes and modifications without departing from the spirit and scope of the present invention. Therefore, the protection scope of the present invention shall be determined by the definition of the claims.

Claims

1. A field sampling method for multiple points in a large area in the wild, characterized in that: The following steps are involved: Step 1, segmenting 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. In the sampling area, the sampling well is defined as a first sampling point, the sampling point in the second area is defined as a second sampling point, and the sampling point in the first area is defined as a third sampling point; Step 2, using different sampling containers for each sampling point to perform gas sampling, wherein a first container (11) is used for sampling at the first sampling point, a second container (12) is used for sampling at the second sampling point, and a third container (13) is used for sampling at the third sampling point; Step 3: Pre-treat the gas samples collected from each container, and perform chromatography, mass spectrometry and carbon dioxide isotope analysis on the collected gas samples on site to obtain the concentrations of hydrogen and helium as well as the carbon dioxide concentration and carbon dioxide isotope ratio in the current gas samples; Step 4: flush the pretreatment and analysis pipelines with nitrogen to exhaust the residual gas samples in the pretreatment and analysis pipelines; Step 5: Repeat steps 2 to 4 until all sampling points are tested. In step 3, the gas analysis system (30) performs on-site analysis on the received gas sample, and the pre-processing 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 wild according to claim 1 is characterized in that: In step 1, the sampling area is divided into a plurality of sampling units according to a 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 extension direction of the road.

3. The field sampling method for large areas and multiple points in the wild according to claim 2 is characterized in that: In step 2, in 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 wild according to claim 1 is characterized in that: In step 2, the first container (11) includes a steel cylinder, which is used to store a gas sample at a first pressure. The second container (12) includes a flexible air bag, which is used to store a gas sample at a second pressure, wherein the second pressure is less than the first pressure. The third container (13) includes an air extraction pipeline, and the air extraction pipeline and the soil layer to be sampled constitute a soil sample collection container.

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

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

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

8. The field sampling method for large areas and multiple points in the wild 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 movable platform; the movable platform comprises a wheeled chassis; the gas extraction device (21) is detachably connected to the wheeled chassis; and the total gas path capacity of each injection path in the pretreatment system (20) and the gas analysis system (30) is less than 30 ml.

9. The field sampling method for multiple points in a large area in the wild according to claim 8, characterized in that: In step 4, after each gas detection, the pipelines in the pre-treatment system (20) and the gas analysis system (30) are evacuated and filled with nitrogen.

10. The field sampling method for multiple points in a large area in the wild according to claim 9, characterized in that: The gas analysis system (30) comprises a chromatography system, a mass spectrometry system, a spectral system, a data acquisition system and an exhaust gas treatment system, wherein the mass spectrometry system is equipped with an independent turbomolecular pump and an electronic pressure controller; The turbomolecular pump is used to evacuate the gas in the pipelines of the pre-treatment system (20) and the gas analysis system (30), and the electronic pressure controller is used to fill nitrogen into the pipelines of the gas analysis system (30) and the pre-treatment system (20).

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