Mobile while-drilling soil gas detection system and wide concentration range detection method

Abstract

The invention relates to the technical field of pollutant detection, in particular to a movable while-drilling soil gas detection system and a wide concentration range detection method.The movable while-drilling soil gas detection system comprises a movable platform, a detection device and a control device, and the movable platform comprises a loading platform and driving wheels connected to the loading platform; and the drilling part is carried on the loading platform. An inert gas compensation mechanism is introduced, the proportion of inert gas of the sample introduction system is dynamically adjusted, the flow of a high-concentration sample is diluted, and the concentration of pollutants at an inlet of the detection module is reduced through the gas dilution module arranged in the sample introduction module, so that the effective detection range of the detection module is expanded, and a low-detection-limit detector can be selected; on the premise of not losing the sensitivity of a low-concentration sample, high-concentration signal overload is inhibited, continuous detection of pollutants in a wide concentration range is realized, both trace identification and high-concentration anti-saturation capability are considered, and the analysis applicability of a complex polluted site is remarkably improved.

Description

Technical Field

[0001] The present invention relates to the technical field of pollutant detection, and in particular to a mobile soil gas detection system while drilling and a wide concentration range detection method. Background Art

[0002] In response to the problems of low efficiency, insufficient accuracy, destructive sampling and cross-layer contamination risks in traditional contaminated site investigation technologies, and combining the advantages of soil gas detection in reflecting pollution conditions and environmental risks, technicians have developed downhole soil gas detection equipment. This overcomes the defects of traditional soil gas monitoring wells, such as limited well construction depth and inability to monitor in real time, and realizes in-situ downhole detection of underground pollutants.

[0003] Currently, in-situ downhole detection technology for contaminated sites is limited by the narrow dynamic range of the detector. To ensure sensitive detection of low-concentration targets, a low-detection-limit detector is usually selected. If high-concentration pollutants are encountered, signal saturation is likely to occur. If a high-detection-limit detector is selected, low-concentration samples may be missed due to insufficient sensitivity, making it difficult to adapt to the application needs of complex contaminated sites with significant differences in pollution concentrations. Summary of the Invention

[0004] In view of the technical problems existing in soil gas detection in the prior art, the first aspect of the present invention proposes a mobile soil gas detection system while drilling, comprising:

[0005] a movable platform comprising a loading platform and drive wheels connected to the loading platform;

[0006] A drilling component is mounted on the loading platform, the drilling component including a detection-while-drilling probe and a direct-push drill rig for driving the detection-while-drilling probe in and out, the detection-while-drilling probe being configured to be driven by the direct-push drill rig to drill into a soil layer at a predetermined depth and collect a gas sample of the current soil layer;

[0007] a sampling module connected to the detection while drilling probe and used to process the gas sample entering the sampling module;

[0008] A sample collection module, connected to the sampling module, for collecting and storing the gas sample entering the sampling module;

[0009] A detection module, connected to the sampling module, for detecting the type and concentration of the target gas in the gas sample in the sampling module in real time;

[0010] An air circuit control module includes a distribution valve, wherein the distribution valve includes two air inlet ends and multiple air outlet ends;

[0011] a gas supply module connected to the distribution valve and configured to respectively supply hydrogen and inert gas to the two gas inlet ports of the distribution valve, and multiple gas outlet ports of the distribution valve to respectively supply target types and flow rates of gas to the drilling system, the sampling module, and the detection system;

[0012] A controller connected to the movable platform, the drilling component, the sampling module, the sample collection module, the detection module, the gas circuit control module, and the gas supply module;

[0013] The sampling module includes a gas dilution module, wherein a first flow meter is provided upstream of the gas dilution module and a second flow meter is provided downstream of the gas dilution module, and the gas dilution module is used to add a predetermined amount of inert gas to the gas sample and maintain the same gas flow through the first flow meter and the second flow meter;

[0014] The upper limit of detection of the detection module is defined as S max The detection limit is S min The controller is configured to detect the target gas concentration signal value S and S in real time according to the detection module. max and S min The relationship between the gas dilution module and the inert gas is controlled to adjust the proportion of the inert gas in the gas sample so that the target gas concentration signal value S in the gas sample entering the detection module is within a preset range.

[0015] Preferably, the gas dilution module is configured to be configured to be activated when the target gas concentration signal value S is greater than or equal to 80% of S max or ≤5S min When adjusting the ratio of inert gas in the gas sample;

[0016] Among them, D n =D n-1 ×S / S t , D n is the adjusted dilution factor, D n-1 is the dilution factor before adjustment, the initial state D n-1 is 1, S t is the target signal value, S t is the geometric mean of the upper limit and the lower limit, and S is the target gas concentration signal value actually detected by the detection module.

[0017] Preferably, the result gain of the detection module is set to be synchronously adjusted according to the dilution multiple of the gas sample by the gas dilution module;

[0018] Among them, G n =D n , G n is the result gain of the adjusted detection module.

[0019] Preferably, the gas dilution module includes a Y-shaped pipe, the Y-shaped pipe includes a first input pipe, a second input pipe and an output pipe, the first input pipe is provided with a first flow valve and an exhaust pipe, and the second input pipe is provided with a second flow valve;

[0020] Among them, the first input pipe is connected to the probe outlet pipe, which is used to receive the gas sample entering from the probe outlet pipe, the first flow valve is used to control the first part of the gas sample to enter the output pipe, and the second part of the gas sample to enter the exhaust pipe, the second input pipe is connected to the outlet end of the distribution valve, and the second flow valve is used to control the flow of inert gas entering the second input pipe.

[0021] Preferably, the controller is configured to adjust the openings of the second flow valve and the first flow valve according to a target dilution ratio of the inert gas in the gas sample, so that the gas flow rates of the first flow meter and the second flow meter are consistent.

[0022] Preferably, a hollow fiber drying tube is provided between the first flow meter and the gas dilution module, and the hollow fiber drying tube includes an insulation shell and an outer tube and an inner tube arranged in the insulation shell, the first end of the inner tube is connected to the output end of the first flow meter, and the second end is connected to the input end of the gas dilution module, and a separation chamber is formed between the outer tube and the inner tube, and a backflush gas inlet and a backflush gas outlet are provided on the outer tube, and the backflush gas inlet is connected to the gas outlet end of the distribution valve, so that the flowing inert gas enters the separation chamber, and the inner tube includes a hollow fiber membrane tube for passing water vapor.

[0023] Preferably, the drilling detection probe includes a probe body, a gas sample collection cavity and a selective permeable membrane structure arranged outside the gas sample collection cavity. A probe air inlet pipe and a probe air outlet pipe are also provided in the probe body, and the probe air inlet pipe and the probe air outlet pipe are both connected to the gas sample collection cavity. A heating component is also provided in the probe body, and the heating component is used to heat the gas sample collection cavity.

[0024] Preferably, the direct-push drill is used to control the drilling speed of the probe body, wherein the controller controls the drilling speed of the direct-push drill according to the difference between the real-time temperature of the selective permeable membrane structure and a preset value.

[0025] A second aspect of the present invention provides a technical solution, a mobile soil gas detection method for a wide concentration range while drilling, using the mobile soil gas detection system while drilling, comprising the following steps:

[0026] Step 1: Pipeline cleaning: Use a predetermined flow rate of inert gas to pass into the sampling module, and use the detection module to detect the change of the signal value. If the change amplitude of the signal value within a predetermined period is less than the preset value, the pipeline cleaning is completed;

[0027] Step 2: Calibrate the detection module by introducing external standard gas into the injection module at a constant flow rate. If the change in the detection module signal value within the predetermined time is less than the preset value, and the maximum signal value deviation from the standard value is less than the preset value, the detection module meets the use requirements;

[0028] Step 3: System calibration: Use standard solution to calibrate the system in the selective permeable membrane structure of the drilling detection probe, record the peak conditions of the detection module, and compare them with the standard spectrum, including peak time and maximum peak height parameters. If the preset deviation is not exceeded, the system calibration is completed;

[0029] Step 4: Drill the target point, assemble the extended probe, and control the probe drilling with a direct-push drilling rig. Drill the probe to a predetermined depth, allowing the sample to be transferred from the selective permeable membrane to the detection module before continuing drilling.

[0030] Step 5: After drilling to the predetermined depth, remove the probe rod and probe in sequence, and then perform the system calibration in step 3. If the requirements are met, the test is completed;

[0031] Wherein, in step 4, collecting and detecting the gas sample at the predetermined depth includes the following steps:

[0032] Step 41: purge the gas sample in the gas sample collection chamber into the sampling module using inert gas;

[0033] Step 42: Dehumidify the gas sample entering the sampling module;

[0034] Step 43: The dehumidified gas sample is detected by a detection module, and a detection concentration signal of the current gas sample is obtained;

[0035] When the target gas concentration signal value S detected by the detection module reaches 80% S max Stop drilling immediately, adjust the dilution ratio, and adjust the result gain simultaneously; when the target gas concentration signal value S is less than 5 times S min , stop drilling immediately and adjust the dilution ratio. If the dilution ratio has been adjusted to 1 and cannot be diluted further, drill normally and adjust the result gain synchronously;

[0036] The dilution multiple and result gain adjustment are as follows:

[0037] D n =D n-1 ×S / S t ;

[0038] G n =D n ;

[0039] Among them, S is the target gas concentration signal value actually detected by the detection module, D n is the adjusted dilution factor, D n-1 is the dilution factor before adjustment, the initial state D n-1 1, G n is the result gain of the adjusted detection module, S t is the target signal value, S t is the geometric mean of the upper and lower limits.

[0040] Preferably, in step 4, a gas sample storage step is also included, in which the gas sample in the gas sample collection chamber is purged into the sampling module and stored in an independent gas bag in the sampling module.

[0041] Compared with the prior art, the advantages of the present invention are:

[0042] In view of the significant difference in pollutant concentrations on the site, a low detection limit detector is usually selected to ensure sensitive detection of low-concentration targets. However, high-concentration samples easily exceed the linear range of the detector, resulting in signal saturation and the formation of a "flat-top peak", which affects the quantitative accuracy. To this end, the present application introduces an inert gas compensation mechanism, which dynamically adjusts the proportion of inert gas in the injection system through a gas dilution module arranged in the injection module, dilutes the flow rate of high-concentration samples, and reduces the concentration of pollutants at the inlet of the detection module, thereby expanding the effective detection range of the detection module. An optional low detection limit detector can suppress high-concentration signal overload without losing the sensitivity of low-concentration samples, thereby achieving continuous detection of pollutants in a wide concentration range, taking into account both trace identification and high-concentration anti-saturation capabilities, and significantly improving the analytical applicability of complex contaminated sites. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] The accompanying 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 the sake of 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:

[0044] Figure 1 Schematic diagram of the structure of the mobile soil gas detection system while drilling shown in the present invention;

[0045] Figure 2 Schematic diagram of the structure of the hollow fiber drying tube shown in the present invention;

[0046] Figure 3 Schematic diagram of the structure of the gas dilution module shown in the present invention. DETAILED DESCRIPTION

[0047] In order to better understand the technical content of the present invention, specific embodiments are given and described below with reference to the accompanying drawings.

[0048] {Example 1}

[0049] Combine Figure 1 As shown, the first aspect of the present invention proposes a mobile soil gas detection system while drilling, including a movable platform, a drilling component 10, a sampling module, a sample collection module 30, a detection module 40, a gas circuit control module 50, a gas supply module 60 and a controller.

[0050] In an optional embodiment, the movable platform includes a loading platform and drive wheels connected to the loading platform. The drive wheels can drive the loading platform to a target location. The drive system of the drive wheels can be controlled by a remote controller, including functions such as steering, forward movement, reverse movement, and speed change, meeting remote control movement requirements.

[0051] Among them, the loading platform is used to carry the gas supply module, sampling module, gas path control module, detection module, data acquisition module and computer terminal, etc.

[0052] Furthermore, the drilling component 10 is loaded onto the loading platform. The drilling component 10 includes a downhole detection probe and a direct-push drilling rig that drives the downhole detection probe to drill and pull out. The downhole detection probe is configured to be driven by the direct-push drilling rig to drill into a soil layer of a predetermined depth and collect gas samples of the current soil layer.

[0053] Preferably, a direct-push drill is used to control the drilling speed of the probe body, wherein the controller controls the drilling speed of the direct-push drill according to the difference between the real-time temperature of the selectively permeable membrane structure 12 and a preset value.

[0054] It should be understood that temperature affects the volatilization of organic pollutants. When the actual heating temperature of the selective permeable membrane does not match the preset value, the drilling speed should be adjusted appropriately. Specifically:

[0055] When 10>Δ T ≥5, V n =V n-1 -a%Δ T ; When 20>Δ T ≥10, V n =V n-1 -b%Δ T If Δ T ≥20, stop drilling immediately and wait for Δ T <5, resume drilling.

[0056] Among them, |Δ T | is the absolute value of the difference between the actual temperature and the preset temperature; a and b are the drilling speed adjustment coefficients, V n and V n-1 They are the adjusted drilling speed and the previous drilling speed, respectively. 2cm / s≥Vn ≥0cm / s.

[0057] Optionally, the downhole detection probe includes a probe body, a gas sample collection chamber 11, and a selective permeable membrane structure 12 arranged outside the gas sample collection chamber 11. A probe air inlet pipe 14 and a probe air outlet pipe 15 are also provided in the probe body. The probe air inlet pipe 14 and the probe air outlet pipe 15 are both connected to the gas sample collection chamber 11. A heating component 13 is also provided in the probe body, and the heating component 13 is used to heat the gas sample collection chamber 11.

[0058] Optionally, the gas sample collection chamber 11 is a metal heating chamber. The selective permeable membrane structure 12 is composed of a substrate, a metal mesh, and a membrane material. The metal mesh is fixed to the substrate by welding and is completely coated with the membrane material. The membrane material is waterproof and breathable, and has a certain barrier effect on inert small molecules such as nitrogen, while being able to pass most volatile organic pollutants.

[0059] Furthermore, an electric heating component is provided for heating the probe air inlet pipe 14 and the probe air outlet pipe 15 , for example, a resistance wire is provided around the pipeline for heating.

[0060] Combine Figure 1 As shown, when the downhole detection probe is driven by a direct-push drill to drill into the ground to a predetermined depth, the heating component 13 and the electric heating components around the pipeline are used to heat the gas sample collection chamber 11 and the surrounding gas pipelines, and enter the gas sample collection chamber 11, and the carrier gas is brought into the gas sample collection chamber 11 by the probe air inlet pipe 14, and the sample gas is brought into the probe air outlet pipe 15 and output to the sampling module, and then detected by the detection module 40.

[0061] In this way, by setting up a heating component 13 and an electric heating component, the soil gas transmission pipeline (probe air inlet pipe 14, probe air outlet pipe 15) can be heated. While reducing the sample transmission loss, accelerated purging can be combined to achieve rapid pipeline aging and accelerate system stability. At the same time, the heating of the transmission line can effectively reduce the loss of volatile organic pollutants, solving the problem of large soil gas transmission pollutant loss and long pipeline aging time.

[0062] Among them, the sampling module is connected to the drilling detection probe, which is used to process the gas sample entering the sampling module; the sample collection module 30 is connected to the sampling module, which is used to store the gas sample entering the sampling module; the detection module 40 is connected to the sampling module, which is used to detect the type and concentration of the target gas in the gas sample in the sampling module in real time.

[0063] Optionally, the detection module 40 includes PID, FID, XSD, and ECD detectors. The sample first enters the PID detector and is then diverted into the FID, XSD, ECD and other detectors. The FID detector is connected to the gas circuit control module 50 through a metal gas pipe to receive hydrogen provided by the gas supply module 60.

[0064] Optionally, the sample collection module 30 includes a sample collection tube, a low-temperature preservation box, and an air bag. The first end of the sample collection tube is connected to the sampling module, and the second end is connected to the air bag, which is used to collect the gas sample discharged from the gas sample collection cavity 11. The low-temperature preservation box is a hollow structure with an air bag placed inside for low-temperature preservation of the air bag to reduce the loss of volatile organic compounds.

[0065] Combine Figure 1 As shown, the sampling module includes a gas dilution module 23, a first flow meter 21 is provided upstream of the gas dilution module 23, and a second flow meter 24 is provided downstream of the gas dilution module 23. The gas dilution module 23 is used to add a predetermined amount of inert gas to the gas sample and keep the gas flow through the first flow meter 21 and the second flow meter 24 the same.

[0066] In this way, the pressure in the entire sampling pipeline will not change, which helps to maintain the pressure balance of the gas path and makes the measurement result of the detection module 40 more accurate.

[0067] Furthermore, a hollow fiber drying tube 22 is provided between the first flowmeter 21 and the gas dilution module 23. Thus, the hollow fiber drying tube 22 can dehumidify the gas sample entering the detection module 40 and remove moisture, thereby preventing abnormal fluctuations in the detection module 40 signal value caused by water vapor entering the pipeline.

[0068] Specific, combined Figure 2 As shown, the hollow fiber drying tube 22 includes an insulating shell 221 and an outer tube 222 and an inner tube 223 arranged in the insulating shell 221. The first end of the inner tube 223 is connected to the output end of the first flowmeter 21, and the second end is connected to the input end of the gas dilution module 23. A separation chamber is formed between the outer tube 222 and the inner tube 223.

[0069] Among them, the outer tube 222 is provided with a back-blowing gas inlet 227 and a back-blowing gas outlet 226. The back-blowing gas inlet 227 is connected to the gas outlet end of the distribution valve, so that the flowing inert gas enters the separation chamber. The inner tube 223 includes a hollow fiber membrane tube for passing water vapor.

[0070] Furthermore, the heat-insulating shell 221 is used to control the temperature of the hollow fiber gas drying module to ensure the water removal efficiency, and the temperature is generally controlled within 100°C.

[0071] In this way, when the gas sample flows from the first end 224 to the second end 225 of the inner tube 223, due to the inert gas flowing through the outside of the inner tube 223, the humidity in the separation chamber is low and the humidity in the inner tube 223 is high. The water vapor is discharged into the separation chamber through the humidity difference, making the humidity of the gas sample passing through the hollow fiber drying tube 22 lower.

[0072] Furthermore, the gas circuit control module 50 includes a distribution valve, which includes two air inlet ends and multiple air outlet ends. The gas supply module 60 is connected to the distribution valve and is used to provide hydrogen and inert gas to the two air inlet ends of the distribution valve respectively. The multiple air outlet ends of the distribution valve provide target types and flow rates of gas to the drilling system 10, the sampling module and the detection system 40 respectively.

[0073] Specific, combined Figure 1 As shown, the two air inlet ends of the distribution valve are connected to the hydrogen gas source and the inert gas source respectively, and the four air outlet ends of the distribution valve are the first air outlet pipe 51, the second air outlet pipe 52, the third air outlet pipe 53 and the fourth air outlet pipe 54 respectively. The first air outlet pipe 51 is connected to the probe air inlet pipe 14, the second air outlet pipe 52 is connected to the detection module 40, the third air outlet pipe 53 is connected to the gas dilution module 23, and the fourth air outlet pipe 54 is connected to the backwash gas inlet 227 of the hollow fiber drying tube 22.

[0074] In the above embodiment, the controller is electrically connected to the movable platform, the drilling component 10 , the sampling module, the sample collection module 30 , the detection module 40 , the gas circuit control module 50 and the gas supply module 60 .

[0075] In order to effectively control the concentration of organic matter in the gas sample entering the detection module 40 to be within an appropriate range, which helps the sensor to accurately detect the organic matter content, the detection upper limit value of the detection module 40 is defined as S max The detection limit is S min The controller is configured to detect the target gas concentration signal value S and S in real time according to the detection module 40. max and S min The gas dilution module 23 is controlled to adjust the ratio of the inert gas in the gas sample so that the target gas concentration signal value S in the gas sample entering the detection module 40 is within a preset range.

[0076] In this way, by controlling the concentration signal S of the target gas entering the detection module 40, the sensor range can be expanded on the basis of selecting a low detection limit sensor, avoiding the problem of flat peaks in small-range sensors and insensitive detection of large-range sensors. According to the concentration signal S of the target gas entering the detection module 40, the concentration of the target gas is dynamically adjusted, so that the small-range sensor can realize full-process accurate detection of the gas sample concentration.

[0077] In an optional embodiment, the gas dilution module 23 is configured to: max or ≤5S min When adjusting the ratio of inert gas in the gas sample;

[0078] Among them, D n =D n-1 ×S / S t , D n is the adjusted dilution factor, D n-1 is the dilution factor before adjustment, the initial state D n-1 is 1, S t is the target signal value, where S t is equal to the geometric mean of the upper limit and the lower limit, and S is the target gas concentration signal value actually detected by the detection module. n-1 The initial value is 1, indicating no dilution, and the value is greater than or equal to 1. When the result calculated according to the formula is less than 1, it should be calculated according to =1.

[0079] In this way, when the gas sample enters the detection module 40, the concentration of the target gas is detected in real time. When the concentration signal S of the target gas is greater than or equal to 80% S max When the dilution factor is adjusted, the dilution factor D n =D n-1 ×S / S t , so that the concentration of organic matter decreases and returns to the detection range of the sensor.

[0080] At the same time, when the dilution factor of the organic matter increases, the result gain of the detection module 40 is set to be synchronously adjusted according to the dilution factor of the gas sample by the gas dilution module 23;

[0081] Among them, G n =D n , G n is the result gain of the detection module 40 after adjustment.

[0082] In this way, according to the concentration change of organic matter within the detection range of the sensor, the dilution factor of the organic matter is adjusted in real time, and the result gain of the detection module 40 is adjusted at the same time, so that the concentration of organic matter is always below the detection upper limit of the sensor, that is, the sensitivity of the detection is guaranteed, and the flat peak phenomenon caused by excessive concentration peak will not occur. Figure 3 As shown, the gas dilution module 23 includes a Y-shaped pipe 231, which includes a first input pipe 232, a second input pipe 233 and an output pipe 234. The first input pipe 232 is provided with a first flow valve 235 and an exhaust pipe 237, and the second input pipe 233 is provided with a second flow valve 236.

[0083] In this way, when the gas sample containing organic matter enters the Y-shaped pipe 231 from the first input pipe 232, the first flow valve 235 can control the proportion of the gas sample entering the output pipe 234, which determines the organic matter content entering the output pipe 234, and the second input pipe 233 can control the proportion of the inert gas entering the output pipe 234, which determines the dilution multiple of the gas sample.

[0084] Specifically, when the air intake ratio of the first input pipe 232 to the second input pipe 233 is 2:8, the dilution factor of the gas sample is 5 times.

[0085] It should be noted that when the air intake ratio of first input pipe 232 to second input pipe 233 is 1:0, the dilution factor is 1, i.e., no dilution occurs. First input pipe 232 is connected to probe outlet pipe 201 and receives the gas sample entering from probe outlet pipe 201. First flow valve 235 controls the flow of a first portion of the gas sample into output pipe 234 and a second portion into exhaust pipe 237. Second input pipe 233 is connected to the outlet of the distribution valve, and second flow valve 236 controls the flow of inert gas into second input pipe 233.

[0086] Furthermore, the controller is configured to adjust the openings of the second flow valve 236 and the first flow valve 235 according to the target dilution ratio of the inert gas in the gas sample, so that the gas flow rates of the first flow meter 21 and the second flow meter 24 are consistent.

[0087] In this way, on the basis of controlling the dilution ratio of the sample gas, the air intake volume before dilution and the air output volume after dilution are also balanced to ensure that the air flow rate is the same, so as to avoid inaccurate test results caused by changes in flow rate.

[0088] In a specific embodiment, the initial dilution factor is 1. When the result calculated according to the formula is less than 1, it should be calculated as =1, that is, the air intake of the first input pipe 232 is 100% of the total flow rate, and the air intake of the second input pipe 233 is 0%.

[0089] Optionally, in the initial state, Dn-1=1, Gn=1, and the sensor range is 0~Cmax (corresponding to signals 10000~500000).

[0090] When the concentration rises, triggering the first adjustment, the detection signal S reaches 400000 (80% Smax), Dn = Dn-1×S / St = 1×400000 / 70711≈5.66, the dilution factor Dn≈5.66, the gain Gn=5.66, that is, the gas sample is diluted 5.66 times, and the intake flow of the first input pipe 232 and the second input pipe 233 is redistributed. The detection signal drops to 70711 (within the safety range). After gain compensation, the output concentration is correct. At this time, the processable concentration is ≈5.66×Cmax (500000), and the signal remains at 70711, which is much smaller than the signal upper limit value.

[0091] Furthermore, the actual concentration continues to increase, and the diluted signal rises from 70711 to 400000 (triggered again). The current Dn-1≈5.66, the new Dn=5.66×400000 / 70711≈5.66×5.66≈32.0, the updated Dn≈32.0, Gn=32.0, the signal drops to 70711, and the processable concentration≈32.0×Cmax.

[0092] As mentioned above, this method can extend the measuring range and avoid the occurrence of flat peaks.

[0093] {Example 2}

[0094] A second aspect of the present invention provides a technical solution, a mobile soil gas detection method for a wide concentration range while drilling, using the mobile soil gas detection system while drilling, comprising the following steps:

[0095] Step 1: Pipeline cleaning: Inert gas at a predetermined flow rate is introduced into the sampling module, and the detection module 40 detects changes in the signal value. If the amplitude of the signal value change within a predetermined period is less than a preset value, the pipeline cleaning is completed.

[0096] Step 2: Calibrate the detection module 40 by introducing external standard gas into the injection module at a constant flow rate. If the change in the signal value of the detection module 40 within a predetermined time is less than a preset value, and the maximum signal value deviation from the standard value is less than a preset value, the detection module 40 meets the use requirements;

[0097] In step 2, the standard gas should be introduced directly into the detection module 40, and should not pass through the long pipeline of the sampling module to enter the detection module 40, so as to avoid contamination residue in the pipeline.

[0098] Step 3: System calibration: Use a standard solution to calibrate the system in the selective permeable membrane structure 12 of the drilling detection probe, record the peak conditions of the detection module 40, and compare them with the standard spectrum, including the peak time and maximum peak height parameters. If the preset deviation is not exceeded, the system calibration is completed;

[0099] Step 4: Drill the target point, assemble the extended probe, and control the probe drilling with a direct-push drilling rig. Drill the probe to a predetermined depth, and then continue drilling after the sample is transferred from the selective permeable membrane to the detection module 40.

[0100] Step 5: After drilling to the predetermined depth, remove the probe rod and probe in sequence, and then perform the system calibration in step 3. If the requirements are met, the test is completed;

[0101] Wherein, in step 4, collecting and detecting the gas sample at the predetermined depth includes the following steps:

[0102] Step 41: purge the gas sample collection chamber 11 into the sampling module using inert gas;

[0103] Step 42: Dehumidify the gas sample entering the sampling module;

[0104] Step 43: The dehumidified gas sample is tested by the detection module 40;

[0105] When the target gas concentration signal value S detected by the detection module 40 reaches 80% S max When the target gas concentration signal value S is less than 5 times S min When the dilution factor is reached, stop drilling immediately, adjust the dilution factor, and adjust the result gain simultaneously. If the dilution factor has been adjusted to 1 and no further dilution is possible, continue drilling normally.

[0106] The dilution multiple and result gain adjustment are as follows:

[0107] D n =D n-1 ×S / S t ;

[0108] G n =D n ;

[0109] Wherein, S is the target gas concentration signal value actually detected by the detection module 40, and D n is the adjusted dilution factor, D n-1 is the dilution factor before adjustment, the initial state D n-1 is 1, D n-1 The maximum value is also 1, G n is the result gain of the adjusted detection module 40, S t is the target signal value, S t is the geometric mean of the upper and lower limits.

[0110] Furthermore, step 4 includes a gas sample storage step, where the gas purge from the gas sample collection chamber 11 is directed into the sampling module and stored in an independent gas bag within the sampling module. This not only enables real-time testing, but also allows the independent gas bag to collect and store gas samples at the target depth, enabling higher-precision testing in the laboratory.

[0111] In a specific embodiment, the specific detection method is as follows:

[0112] (1) Use the mobile soil gas detection system while drilling as described above and use a movable platform to move the equipment to a designated point.

[0113] (2) After arriving at the designated location, start the equipment, connect each module, and turn on the gas supply module, gas control module, injection module (the injection module is optional and should be turned on when needed), detection module, data acquisition system and computer terminal in turn.

[0114] (3) Quality control before implementation:

[0115] Pipeline aging and baseline calibration: Heat the gas sample collection chamber 11 through the heating component 13 (resistance wire), increase the carrier gas flow rate, and other methods to accelerate the aging of the circuit and detector and eliminate the interference of residual contaminants. During the equipment aging stage, the gas flow rate out of the probe is increased to 150mL / min, the temperature of the gas sample collection chamber 11 is increased to 150℃, and the temperature of the resistance wire is increased to 100℃. After the equipment is aged for 5 minutes, if the change amplitude of all detector signal values ​​is less than 8% within 20 to 50 seconds (that is, the time from the sample entering the detection module 40 from the selective permeable membrane window and generating detection data), it indicates that the residual contaminants have been basically removed and the aging is now complete.

[0116] Lower the metal heating chamber temperature to 80-120°C, the resistance wire temperature to 40-80°C, and the gas flow rate out of the probe to 30-50 ml / min. Wait 5 minutes after the temperature and gas flow rate reach the preset values. If the peak change in all detector signals is less than 5% within 20-50 seconds, the baseline is essentially stable and you can proceed to the next step.

[0117] Calibration of the detection capability of detection module 40: The detection capability of detection module 40 is crucial for the application of downhole inspection equipment. During system calibration, the conversion of liquid phase to gas phase has a large uncertainty, and the acquisition of samples through the selective permeable membrane window has a certain degree of randomness, which may cause insufficient detection capability of the detector to go undetected. Therefore, the detection capability of the detector must be calibrated separately. At the gas sampling end of detection module 40, an external standard gas is introduced at a constant flow rate. The detection data of detection module 40 is recorded, and the maximum signal value and signal change are examined. If the change in the signal value of all detection modules 40 is less than 4% within a certain period of time, and the maximum signal value deviation from the standard value is less than 5%, it indicates that the detection module 40 meets the requirements.

[0118] The standard gas may contain one factor or multiple factors, but it must be ensured that the introduced standard gas can be detected by all detection modules 40 .

[0119] System calibration: simulate underground environment, use standard solution to calibrate the system at the selective permeability membrane window, ensure that the time the standard solution is placed on the selective permeability membrane window is consistent with the time it stays there when the standard spectrum library is established, ensure that the volume of the standard solution is consistent, record the peak situation, and compare it with the standard spectrum, including peak time and maximum peak height parameters.

[0120] Ensure that the flow rate, calibration solution and concentration, and the time the solution is inverted at the selective permeability membrane window are consistent with the standard spectrum library (i.e., the spectrum generated by the calibration solution response test completed before the equipment is installed). Also, consider the differences in test results caused by changes in the initial calibration solution temperature and atmospheric temperature. The peak time error should be less than 4%, and the maximum peak height error is 8% + E.

[0121] E=α*|Δ air |*(T0 / T bp ) k 1+β*|Δ liquid |(T0 / T bp ) k 2

[0122] α and β are the weight coefficients of atmospheric temperature and calibration liquid temperature changes, respectively, which are used to adjust the influence of atmospheric temperature changes and liquid temperature changes on the error.

[0123] k1 and k2 are the pollutant boiling point influence coefficients, which are used to adjust the weight of the impact of boiling point on temperature change.

[0124] E is the error deviation value, which indicates the error deviation caused by the boiling point and temperature changes of the pollutants during the calibration process.

[0125] |Δ air | is the difference between the atmospheric temperature when the standard spectrum library is established and the corresponding temperature during actual detection, |Δ liquid| is the difference between the standard solution temperature corresponding to the establishment of the standard spectrum library and the corresponding temperature during actual detection.

[0126] T bp The boiling point of the pollutant (unit: ℃, must be consistent with the unit of T0). Organic pollutants with a boiling point less than 40℃ are not suitable for use as calibration liquids.

[0127] T0 is the reference boiling point threshold (generally 180-220°C).

[0128] For example, when the standard spectrum library is established, the atmospheric temperature is 25°C and the standard liquid temperature is 20°C. During actual detection, the temperature is 30°C, the standard liquid temperature is 22°C, α is 0.05, β is 0.11, k1 is 1.5, k2 is 2, T0 is 200°C, T bp is 83.5℃, corresponding to |Δ air | and |Δ liquid |5 and 2 respectively.

[0129] E=0.05*5*(200 / 83.5) 1.5 +0.11*2*(200 / 83.5) 2 =0.93+1.26=2.19%

[0130] Under this condition, the maximum peak height error is 8% + E = 8% + 2.19% = 10.19%

[0131] The standard solution is generally a benzene series or a halogenated hydrocarbon, with a concentration between 1 and 100 ppm and a boiling point generally between 40 and 150°C. If it exceeds the error range, it needs to be stabilized and retested until the deviation calibration is passed.

[0132] (4) Assemble the extended probe according to the drilling depth requirements, connect the extended probe that meets the drilling depth in series to the survey line, drill in sequence, and monitor the entire process. The monitoring content includes: drilling speed, system pressure, and temperature.

[0133] ① Drilling speed control: The drilling speed is required to be no more than 2 cm / s, and the drilling speed should be mainly uniform. After drilling for 30 to 50 cm, the sample should be allowed to transfer from the selective permeable membrane to the detection module before continuing drilling.

[0134] ② System pipeline pressure control: During the drilling process, the system pressure should remain basically stable. If the fluctuation range is greater than 4%, there is a leak or blockage in the surface pipeline. Drilling should be stopped immediately and the fault should be checked before drilling again.

[0135] ③ Temperature control: Temperature affects the volatilization of organic pollutants. When the actual heating temperature of the selective permeable membrane does not match the preset value, the drilling speed should be adjusted appropriately. Specifically:

[0136] When 10>ΔT ≥5, V n =V n-1 -a%Δ T ; When 20>Δ T ≥10, V n =V n-1 -b%Δ T If Δ T ≥20, stop drilling immediately and wait for Δ T <5, resume drilling.

[0137] Among them, |Δ T | is the absolute value of the difference between the actual temperature and the preset temperature; a and b are the drilling speed adjustment coefficients, V n and V n-1 They are the adjusted drilling speed and the previous drilling speed, respectively. 2cm / s≥V n ≥0cm / s.

[0138] (5) When drilling to the depth required for sampling, the sample collection mode can be adjusted. The valve of the probe air pipe 201 in the sampling module that flows into the detection module 40 is closed. The low-temperature preservation box of the sample collection module is opened in advance to maintain the temperature inside the box less than or equal to 4°C. The valve of the probe air pipe 201 in the sampling module that flows into the sample collection module 30 is opened to collect gas samples into the air bag. After the air bag load is reached, sampling can continue to be carried out into another air bag. After completion, the point, depth and other information are marked on the air bag. Close the valve of the probe air pipe 201 in the sampling module that flows into the sample collection module 30, and simultaneously open the valve of the probe air pipe 201 in the sampling system that flows into the detection module 40. After waiting for the sample pipeline transmission time, the drilling detection can be continued.

[0139] (6) Gas dilution module operation: When the detector signal value reaches 80% of the maximum limit, drilling should be stopped immediately, the dilution factor should be adjusted, and the result gain should be adjusted simultaneously; when the actual detection signal value is less than 5 times the detection limit, drilling should be stopped immediately, the dilution factor should be adjusted, and the result gain should be adjusted simultaneously, as follows:

[0140] When the target gas concentration signal value S detected by the detection module 40 reaches 80% S max When the target gas concentration signal value S is less than 5 times S min When the drilling is stopped, the dilution factor should be adjusted and the result gain should be adjusted simultaneously;

[0141] The dilution multiple and result gain adjustment are as follows:

[0142] D n =D n-1 ×S / S t ;

[0143] G n =D n ;

[0144] Wherein, S is the target gas concentration signal value actually detected by the detection module 40, and D n is the adjusted dilution factor, D n-1 is the dilution factor before adjustment, the initial state D n-1 is 1, D n-1 The maximum value is also 1, G n is the result gain of the adjusted detection module 40, S t is the target signal value, S t is the geometric mean of the upper and lower limits.

[0145] (7) After drilling to the predetermined depth, stop the time for the sample to be transferred from the selective permeable membrane to the detector, remove the probe rod and drill bit in turn, and perform system calibration according to method (3). If the requirements are met, the test can be ended; if the deviation is large, it needs to be stabilized and then retested; if the deviation is still too large after retesting, the entire equipment should be overhauled. After the overhaul is completed, the point should be retested according to the above steps (1) to (7).

[0146] In combination with the above embodiments, in order to address the problem of insufficient quality control in traditional membrane interface detection technology or detection while drilling technology, as shown in step (3), baseline calibration, detector detection capability calibration, and system calibration means are introduced before and after implementation, and real-time monitoring and coordinated adjustment methods of drilling speed, temperature, and system pressure are introduced during the implementation process to improve the reliability of the overall application of the equipment.

[0147] While the present invention has been disclosed above with reference to preferred embodiments, this is not intended to limit the present invention. Persons skilled in the art will readily appreciate that various modifications and variations can be made without departing from the spirit and scope of the present invention. Therefore, the scope of protection of the present invention shall be determined by the claims.

Claims

1. A mobile soil gas detection system while drilling, characterized in that: include: a movable platform comprising a loading platform and drive wheels connected to the loading platform; A drilling component (10) is mounted on the loading platform, the drilling component (10) comprising a detection while drilling probe and a direct-push drilling rig for driving the detection while drilling probe to drill and pull out, the detection while drilling probe being configured to be driven by the direct-push drilling rig to drill into a soil layer at a predetermined depth and collect a gas sample of the current soil layer; a sampling module connected to the detection while drilling probe and used to process the gas sample entering the sampling module; a sample collection module (30), connected to the sampling module, for collecting and storing the gas sample entering the sampling module; A detection module (40), connected to the sampling module, for detecting the type and concentration of the target gas in the gas sample in the sampling module in real time; An air circuit control module (50) includes a distribution valve, wherein the distribution valve includes two air inlet ends and a plurality of air outlet ends; a gas supply module (60) connected to the distribution valve and used to respectively supply hydrogen and inert gas to the two gas inlet ends of the distribution valve, and multiple gas outlet ends of the distribution valve respectively supply target types and flow rates of gas to the drilling system (10), the sampling module, and the detection system (40); a controller electrically connected to the movable platform, the drilling component (10), the sampling module, the sample collection module (30), the detection module (40), the air path control module (50), and the air supply module (60); The sampling module includes a gas dilution module (23), a first flow meter (21) is provided upstream of the gas dilution module (23), and a second flow meter (24) is provided downstream of the gas dilution module (23), wherein the gas dilution module (23) is used to add a predetermined amount of inert gas to the gas sample and maintain the same gas flow through the first flow meter (21) and the second flow meter (24); The upper limit of detection of the detection module (40) is defined as S max The detection limit is S min The controller is configured to detect the target gas concentration signal value S and S in real time according to the detection module (40). max and S min The gas dilution module (23) is controlled to adjust the ratio of the inert gas in the gas sample so that the target gas concentration signal value S in the gas sample entering the detection module (40) is within a preset range.

2. The mobile soil gas detection system while drilling according to claim 1, characterized in that: The gas dilution module (23) is configured to be configured to be effective when the target gas concentration signal value S is greater than or equal to 80% of S max or ≤5S min When adjusting the ratio of inert gas in the gas sample; Among them, D n =D n-1 ×S / S t , D n is the adjusted dilution factor, D n-1 is the dilution factor before adjustment, and D is the initial state. n-1 is 1, S t is the target signal value, S t is the geometric mean of the upper and lower limits.

3. The mobile soil gas detection system while drilling according to claim 2, characterized in that: The result gain of the detection module (40) is set to be synchronously adjusted according to the dilution factor of the gas sample by the gas dilution module (23); Among them, G n =D n , G n is the result gain of the adjusted detection module (40).

4. The mobile soil gas detection system while drilling according to any one of claims 1 to 3, characterized in that: The gas dilution module (23) includes a Y-shaped pipe (231), the Y-shaped pipe (231) includes a first input pipe (232), a second input pipe (233), and an output pipe (234), the first input pipe (232) is provided with a first flow valve (235) and an exhaust pipe (237), and the second input pipe (233) is provided with a second flow valve (236); The first input pipe (232) is connected to the probe outlet pipe (201) and is used to receive the gas sample entering from the probe outlet pipe (201); the first flow valve (235) is used to control the first part of the gas sample to enter the output pipe (234) and the second part of the gas sample to enter the exhaust pipe (237); the second input pipe (233) is connected to the outlet end of the distribution valve; and the second flow valve (236) is used to control the flow of the inert gas entering the second input pipe (233).

5. The mobile soil gas detection system while drilling according to claim 4, characterized in that: The controller is configured to adjust the openings of the second flow valve (236) and the first flow valve (235) according to a target dilution ratio of the inert gas in the gas sample, so that the gas flow rates of the first flow meter (21) and the second flow meter (24) are consistent.

6. The mobile soil gas detection system while drilling according to claim 1, characterized in that: A hollow fiber drying tube (22) is provided between the first flow meter (21) and the gas dilution module (23), and the hollow fiber drying tube (22) includes a heat-insulating shell (221) and an outer tube (222) and an inner tube (223) arranged in the heat-insulating shell (221). The first end of the inner tube (223) is connected to the output end of the first flow meter (21), and the second end is connected to the input end of the gas dilution module (23). A separation chamber is formed between the outer tube (222) and the inner tube (223). A backflush gas inlet (227) and a backflush gas outlet (226) are provided on the outer tube (222). The backflush gas inlet (227) is connected to the gas outlet end of the distribution valve, so that the flowing inert gas enters the separation chamber. The inner tube (223) includes a hollow fiber membrane tube for permeating water vapor.

7. The mobile soil gas detection system while drilling according to claim 1, characterized in that: The drilling detection probe comprises a probe body, a gas sample collection cavity (11), and a selective permeation membrane structure (12) arranged outside the gas sample collection cavity (11); a probe air inlet pipe (14) and a probe air outlet pipe (15) are also provided in the probe body; the probe air inlet pipe (14) and the probe air outlet pipe (15) are both connected to the gas sample collection cavity (11); a heating component (13) is also provided in the probe body; the heating component (13) is used to heat the gas sample collection cavity (11).

8. The mobile soil gas detection system while drilling according to claim 7, characterized in that: The direct-push drilling rig is used to control the drilling speed of the probe body, wherein the controller controls the drilling speed of the direct-push drilling rig according to the difference between the real-time temperature of the selective permeable membrane structure (12) and a preset value.

9. A mobile method for detecting soil gas in a wide concentration range while drilling, characterized in that: Using the mobile soil gas detection while drilling system according to any one of claims 1 to 8 comprises the following steps: Step 1: Pipeline cleaning: inert gas at a predetermined flow rate is introduced into the sampling module, and the change of the signal value is detected by the detection module (40). If the amplitude of the signal value change within a predetermined period is less than a preset value, the pipeline cleaning is completed; Step 2: Calibrate the detection module (40), introduce external standard gas into the sampling module at a constant flow rate, and if the amplitude of the change of the signal value of the detection module (40) within a predetermined time is less than a preset value, and the amplitude of the change of the maximum signal value deviation from the standard value is less than a preset value, then the detection module (40) meets the use requirements; Step 3: System calibration: Use a standard solution to calibrate the system in the selective permeable membrane structure (12) of the drilling detection probe, record the peak of the detection module (40), and compare it with the standard spectrum, including the peak time and maximum peak height parameters. If it does not exceed the preset deviation, the system calibration is completed; Step 4: Drilling the target point, assembling the extended probe, and controlling the probe to drill using a direct-push drilling rig. After drilling to a predetermined depth, the drilling is continued after a time period sufficient for the sample to be transferred from the selective permeable membrane to the detection module (40); Step 5: After drilling to the predetermined depth, remove the probe rod and probe in sequence, and then perform the system calibration in step 3. If the requirements are met, the test is completed; Wherein, in step 4, collecting and detecting the gas sample at the predetermined depth includes the following steps: Step 41: The pollutants collected in the gas sample collection chamber (11) are purged into the sampling module by an inert gas; Step 42: Dehumidify the gas sample entering the sampling module; Step 43: Detecting the dehumidified gas sample through the detection module (40) and obtaining a detection concentration signal of the current gas sample; When the target gas concentration signal value S detected by the detection module (40) reaches 80% S max Stop drilling immediately, adjust the dilution ratio, and adjust the result gain simultaneously; when the target gas concentration signal value S is less than 5 times S min , stop drilling immediately, adjust the dilution factor, and adjust the result gain simultaneously. If the dilution factor has been adjusted to 1 and no further dilution is possible, then drill normally; The dilution multiple and result gain adjustment are as follows: D n =D n-1 ×S / S t ; G n =D n ; Wherein, S is the target gas concentration signal value actually detected by the detection module (40), D n is the adjusted dilution factor, D n-1 is the dilution factor before adjustment, and D is the initial state. n-1 1, G n is the result gain of the adjusted detection module (40), S t is the target signal value, S t is the geometric mean of the upper and lower limits.

10. The mobile method for detecting soil gas while drilling over a wide concentration range according to claim 9, characterized in that: In step 4, a gas sample collection and storage step is also included, in which the sample in the gas sample collection chamber (11) is purged into the sampling module and stored in an independent gas bag in the sampling module.

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