CN115597927A - A kind of monitoring sampling device and monitoring sampling method of soil gas composition - Google Patents

Abstract

The invention proposes a monitoring and sampling device and a monitoring and sampling method for soil gas components. The monitoring and sampling device includes: a sampling tube, an injection tube, a differential pressure measuring device, a vacuum pump, a constant volume container, a monitoring container and a gas sensor, and the lower part of the monitoring container is inserted into the In the soil, a water permeable membrane is provided near the bottom of the monitoring container, and a water inlet porous section is provided on the side wall. The present invention acquires underground fluid samples in the monitoring area at multiple points to realize matrix-type large-area monitoring. Through the cooperation of sample data and gas sensors, the information of abnormal points in the soil can be quickly understood, and multi-point sample mixed sampling can be compared with single-point sampling. Combined with detailed monitoring of the changes in the composition and gas content of soil gas; the present invention can adjust the shallow underground soil environment and atmosphere in the monitoring area by injecting modified gas; section, to achieve normal monitoring in flooded environments.

Description

A kind of monitoring sampling device and monitoring sampling method of soil gas composition

technical field

The invention relates to the technical field of soil monitoring, in particular to a monitoring and sampling device and a monitoring and sampling method for soil gas components.

Background technique

There are Rn, He, O ₂ , N ₂ , H ₂ , CO ₂ , NH ₃ , CH ₄ , N ₂ O and other gases in the soil. Under different soil environments, the main components of soil gas are also significantly different. Understanding soil gas The proportion of each substance in the soil has a significant effect on the study of soil environment. The increase in the concentration of greenhouse gases in the atmosphere is the main factor leading to global warming. CO ₂ , NH ₄ , and N ₂ O in the atmosphere are the main gases that cause the greenhouse effect or global warming. Monitoring CO ₂ , CH ₄ , and N in the soil environment The content of ₂ O and other gases can be effectively used in environmental monitoring and other fields to find out their sources, sinks and migration pathways, while CO ₂ , H ₂ , CH ₄ , He, Rn and other gases with deep source information In all circles of the earth, the gas in the deep part of the earth is most likely to escape upward during the crust and mantle activities. The formation fault zone is a good channel for various gases to escape underground. The change of their concentration can sensitively and objectively reflect the change of the fault activity. , monitoring the composition of the above gases can understand the movement of underground faults, and can be used in the fields of earthquake prediction and stratigraphic research.

In order to alleviate the greenhouse benefit and energy problems, human beings have carried out a lot of research and carried out field experiments of CO ₂ geological storage such as CCS, CO ₂ -EOR, and CO ₂ -ECBM. In order to verify the storage effect of the above experiments, the underground soil environment and changes in the composition of Rn, He, O ₂ , N ₂ , H ₂ , CO ₂ , NH ₃ , CH ₄ , and N ₂ O in the underground soil environment and soil gas were explored, whether it was monitoring CO ₂ , etc. The safety of sealed gas leaking along faults is particularly important in other geological surveys such as mine adjustment, earthquake monitoring, and environmental monitoring. The proportion of the above-mentioned gases in the soil varies greatly, and the solubility of different gases in water also varies. Monitoring The accuracy of the methods and monitoring instruments is also significantly different, and the moisture content in the formation and soil under different water levels will affect the monitoring of the above gas components. The water content, permeability, pH, plant root system and physiological metabolism of microorganisms in the underground soil will all affect the composition and emission of soil gas. Changes in soil moisture will affect the aeration of the soil, and it is necessary to promote or hinder the diffusion of CO ₂ produced in the soil and CO ₂ leaked underground. As the moisture content of the soil increases, the permeability of the soil also decreases. In the flooded environment, ordinary monitoring instruments cannot be used due to the water level. In the past, the method of monitoring the soil environment (such as pH, ORP), physical parameters (porosity, permeability coefficient) and soil gas content was usually collected after on-site sampling. Laboratory analysis, monitoring the soil environment through laboratory data, or using expensive experimental instruments for on-site surveys, it is difficult to monitor the changes in soil environment and gas composition in real time, and it is also difficult to take large-scale multi-point sampling and monitoring, and it is impossible to understand the monitoring in detail in a timely manner Due to the changes in the underground soil environment and soil gas in the area, it is difficult to carry out targeted modification of the shallow soil environment through the above methods, and it is also impossible to conduct large-scale monitoring in the shallow stratum, and it is impossible to obtain the comprehensive apparent parameters of the stratum (permeability coefficient, water level and other parameters), the content and flow rate of each gas in the gas sample.

Therefore, the following technical difficulties need to be overcome at present: how to improve the monitoring efficiency of underground soil environment and soil gas composition changes, how to quickly and effectively monitor the underground soil environmental water level, permeability coefficient, moisture content and other apparent characteristics and formation soil gas Rn, He, The proportion of O ₂ , N ₂ , H ₂ , CO ₂ , NH ₃ , CH ₄ , N ₂ O and other components, how to overcome the impact of waterlogging and submersion environment on monitoring devices, and how to influence the shallow formation environment and The soil gas composition is monitored in a large area with multiple points and parameters, and the monitored soil environment and soil gas composition are used to understand the physical and chemical changes in the underground of the monitoring area, and how to modify the soil atmosphere based on the monitoring data.

Contents of the invention

The purpose of the present invention is to provide a monitoring and sampling device and sampling method for soil gas components, which can overcome the influence of waterlogged and submerged environment on the monitoring device, and can perform multi-parameter monitoring on the shallow underground formation environment in a large area. Comprehensive appearance parameters (permeability coefficient k, water level, etc.), the proportion of each gas component and gas flow rate are used to understand the physical and chemical changes in the underground of the monitoring area.

An embodiment of the present application proposes a monitoring and sampling device for soil gas components, including: a monitoring container and a sampling tube, the lower part of the monitoring container is inserted into the soil, the lower end of the monitoring container is provided with an opening, and the position of the monitoring container above the opening is A water permeable device is provided, a water inlet porous section is arranged on the side wall of the monitoring container, and the water inlet porous section is arranged above the water permeable device, and a gas sensor is arranged in the monitoring container, and the gas sensor is arranged above the water inlet porous section.

One end of the sampling tube is connected to a monitoring container, the other end of the sampling tube is connected to a vacuum pump, a differential pressure measuring device and a constant volume container are connected on the sampling tube between the monitoring container and the vacuum pump, and the constant volume container is connected to the differential pressure measuring device and the vacuum pump. between vacuum pumps.

In this application, a water-permeable device and a water inlet porous section are arranged on the monitoring container to prevent the monitoring and sampling effect from being submerged inside the monitoring and sampling device when the water level is high, so that the monitoring and sampling device can monitor normally in a flooded environment. When the water level is normal, the moisture and gas in the soil slowly enter the monitoring container through the water inlet porous section and the permeable membrane until the sample environment inside the monitoring container is consistent with the soil environment. When the water level is too high, excess water enters the monitoring container through the water inlet porous section, and is discharged to the soil through the permeable membrane on the bottom surface, so as to control the internal water level of the monitoring container.

This application can quickly understand the information of abnormal points in the soil through the cooperation of sample data and gas sensors, and can combine multi-point sample mixed sampling with single-point sampling to monitor the changes in soil gas composition and gas content in detail.

In some embodiments, the water permeable device is a water permeable membrane. The permeable membrane is a two-way permeable membrane. The water-permeable membrane is a hydrophilic material, and moisture can pass through the water-permeable membrane normally.

In some embodiments, the water-permeable membrane is installed in the monitoring container through a bracket, and the bracket is arranged under the water-permeable membrane. The function of the support is to support the permeable membrane, so that there is a certain space between the permeable membrane and the soil, so as to prevent the sand and stone from piercing the permeable membrane after the permeable membrane contacts with the soil.

In some embodiments, the water inlet porous section is made of ceramic or metal. The water inlet porous section is fixedly embedded on the side wall of the monitoring container. Further, the metal can be made of stainless steel to prevent rust.

In some embodiments, an injection tube is also included, the injection tube is inserted into the monitoring container. According to the monitored shallow underground stratum and the apparent parameter information of the soil environment (such as permeability coefficient, water level, pH, gas content ratio, etc.), the modified gas can be injected into the monitoring container through the injection pipe, and the shallow Modification of the soil environment.

In some embodiments, the sampling tube and the injection tube are respectively sealed and connected to the upper part of the monitoring container. The closed structure of the monitoring container prevents other gases in the air from affecting the soil gas monitoring and protects the gas sensor.

In some embodiments, the differential pressure measuring device includes a damping tube, a one-way valve, and a differential pressure gauge for measuring the pressure difference between the front and rear ends of the damping tube, and the damping tube and the one-way valve are connected between the monitoring container and the constant volume container In between, the one-way valve is connected between the damping tube and the constant volume container, and the differential pressure gauge is connected in parallel to the sampling tubes at the front and rear ends of the damping tube through branch tubes. The structure of a differential pressure measuring device is provided, which can replace commercially available differential pressure flowmeters and can reduce costs.

Among them, the differential pressure gauge is used to measure the pressure difference between the front and rear ends of the damping pipe. As time goes by, the pressure difference on both sides of the damping pipe will automatically decay. According to the decay curve of the pressure difference, the permeability of the underground soil environment can be judged.

The one-way valve is a standard one-way valve, and its direction is a fixed direction from the underground soil to the constant volume container. The one-way valve can prevent the fluid in the external air from flowing back into the monitoring container above the soil at the monitoring point to pollute its internal sample environment. It affects the specific value of each gas component and the pressure decay in the device, and the installation of a one-way valve can increase the vacuuming effect of the vacuum pump and the representativeness of collecting underground fluid samples.

The damping tube is a capillary tube with fixed permeability, a porous tube, or a material with a fixed permeability coefficient such as various rock cores, which can increase the pressure decay time after the monitoring sampling device is evacuated, and generate pressure at the front and rear sides of the damping tube. Differential pressure, the pressure difference attenuation on both sides of the damping tube is monitored by the differential pressure gauge. In the case of a fixed permeability coefficient of the damping tube, the permeability of the underground soil environment can be judged according to the different pressure difference attenuation curves of the damping tube The characteristics of the underground environment and the water level are retrieved based on the gas sample analysis data.

In some embodiments, the differential pressure measuring device is a differential pressure flow meter. The commercially available differential pressure flowmeter replaces the above-mentioned differential pressure flow device, which can be directly installed in the monitoring and sampling device, thereby simplifying the structure.

In some embodiments, the sampling pipe is provided with a first control valve, the first control valve is provided between the vacuum pump and the constant volume container, and the injection pipe is provided with a second control valve. The first control valve is used to control the on-off of the sampling pipe, and the second control valve is used to control the on-off of the injection pipe.

Another embodiment of the present application proposes a method for monitoring and sampling soil gas components, using the above-mentioned monitoring and sampling device for soil gas components, including the following steps:

S1, arrange several monitoring and sampling devices at different monitoring positions in the monitoring area, initially monitor the soil gas composition and content at each monitoring position through gas sensors, and observe whether the monitoring data is abnormal;

S2, when the data monitored by the gas sensor at a certain monitoring position is abnormal, open the first control valve and vacuum pump of the monitoring sampling device at the monitoring position, sample the soil gas at the monitoring position, and pump the soil gas to a constant volume Conduct further experimental analysis in the container, and judge the permeability of the soil environment through the monitoring data of the differential pressure measuring device;

S3, judge whether the soil in the monitoring area needs to be modified according to the experimental analysis data. When the soil in the monitoring area needs to be modified, determine the factors that need to be modified, open the injection pipe, and pass the modified gas into the monitoring container through the injection pipe. The modified gas enters the soil outside the monitoring container through the water inlet porous section for modification.

In some embodiments, several monitoring and sampling devices are arranged in a matrix in the monitoring area to form a matrix monitoring. Through multi-point acquisition of underground fluid samples in the monitoring area, matrix large-area monitoring can be realized, and the apparent permeability of underground soil can be obtained through multi-point monitoring, and the change of underground comprehensive parameters can be fed back in time. Combined with the geological model, a relatively fine inversion can be realized Underground parameters (water level, permeability coefficient, water content, content and proportion of each gas) and structural movement state, inversion of the location of the underground leakage point and the possible leakage amount.

The beneficial effects of the present invention are:

(1) The present invention prevents the monitoring and sampling effect from being submerged inside the monitoring and sampling device when the water level is high by arranging a water-permeable device and a water inlet porous section on the monitoring container, so that the monitoring and sampling device can monitor normally in a water-soaked environment ;

(2) The present invention can quickly understand the information of abnormal points in the soil through the cooperation of sample data and gas sensors, and can combine multi-point sample mixed sampling with single-point sampling to monitor the changes in soil gas components and gas content in detail ;

(3) The present invention acquires underground fluid samples in the monitoring area through multiple points, realizes matrix large-area monitoring, and obtains the apparent permeability of underground soil through multi-point monitoring, and timely feedbacks changes in underground comprehensive parameters, which can be realized in combination with geological models More precise inversion of underground parameters (water level, permeability coefficient, water content, content and proportion of each gas) and structural movement state, inversion of the location of underground leakage points and possible leakage volume;

(4) According to the monitoring data, the present invention can choose to inject modified gas to adjust the shallow underground soil environment and atmosphere in the monitoring area.

Description of drawings

The above and/or additional aspects and advantages of the present invention will become apparent and easy to understand from the following description of the embodiments in conjunction with the accompanying drawings,

in:

Fig. 1 is the structural representation of the monitoring sampling device of soil gas composition in the embodiment of the present application;

FIG. 2 is a schematic diagram of a matrix arrangement of monitoring and sampling devices in an embodiment of the present application;

Fig. 3 is the soil differential pressure attenuation curve of different permeability in the embodiment 1 of the present application;

Reference signs:

1-injection pipe; 2-second control valve; 3-gas sensor; 4-monitoring container; 5-inlet porous section; 6-permeable membrane; 7-sampling tube; 8-damping tube; 10-one-way valve; 11-constant volume container; 12-first control valve; 13-vacuum pump; 14-soil; 15-water level; 16-monitoring sampling device.

detailed description

Embodiments of the invention are described in detail below, examples of which are illustrated in the accompanying drawings. The embodiments described below by referring to the figures are exemplary and are intended to explain the present invention and should not be construed as limiting the present invention.

The monitoring and sampling device and monitoring and sampling method of soil gas composition according to the embodiments of the present invention will be described below with reference to the accompanying drawings.

As shown in Figure 1, an embodiment of the present application proposes a monitoring and sampling device for soil gas composition, comprising: a monitoring container 4 and a sampling tube 7, the lower part of the monitoring container 4 is inserted into the soil 14, and the lower end of the monitoring container 4 is provided with Opening, the monitoring container 4 is provided with a water permeable device at the position above the opening, the side wall of the monitoring container 4 is provided with a water inlet porous section 5, the water inlet porous section 5 is arranged above the water permeable device, and the monitoring container 4 is provided with a gas sensor 3. The gas sensor 3 is set above the water inlet porous section 5 .

One end of the sampling tube 7 is connected to the monitoring container 4, and the other end of the sampling tube 7 is connected to the vacuum pump 13, which is a standard product and provides power for soil gas sampling. The sampling pipe 7 between the monitoring container 4 and the vacuum pump 13 is connected with a differential pressure measuring device and a constant volume container 11 , and the constant volume container 11 is connected between the differential pressure measuring device and the vacuum pump 13 . Among them, the constant volume container 11 can increase the internal volume of the monitoring and sampling device, can store soil samples in the monitoring area and increase the amount of samples during each fluid sampling, and its volume can be determined according to monitoring and sampling requirements, which can be 1L, 2L or Other specifications.

In some specific embodiments, the monitoring container 4 is cylindrical. The opening of the lower part of the monitoring container 4 is directly connected to the ground soil 14. The monitoring container 4 is covered above the monitoring point. The upper part of the monitoring container 4 is connected with the sampling pipe 7 and the injection pipe 1 to form a closed structure. The gas sensor 3 is installed inside the monitoring container 4. The monitoring container 4 is provided with a water inlet porous section 5 and a water permeable device, the moisture in the stratum will enter the inside of the monitoring container 4 through the water inlet porous section 5, and the gas in the formation can also pass through the water inlet porous section after reaching the depth of the water inlet porous section 5 5 into the monitoring container 4, the excess water will be discharged through the water permeable device at the bottom, the water can pass through the water permeable device normally, the water inlet porous section 5 and the water permeable device can control the water level 15 inside the monitoring container 4 to remain in the water inlet porous section 5 to prevent waterlogging from affecting the inside of the monitoring container 4.

In some specific embodiments, the water inlet porous section 5 is arranged in the middle section of the monitoring container 4 .

In some specific embodiments, the water permeable device is a water permeable membrane 6 . The water-permeable membrane 6 is a two-way water-permeable membrane. The water-permeable membrane 6 is a hydrophilic material, and moisture can pass through the water-permeable membrane 6 normally.

In some specific embodiments, the water-permeable membrane 6 is installed in the monitoring container 4 through a bracket, and the bracket is arranged below the water-permeable membrane 6 . The function of the support is to support the permeable membrane 6, so that there is a certain space between the permeable membrane 6 and the soil, so as to prevent the permeable membrane 6 from being pierced by sand and gravel after the permeable membrane 6 contacts with the soil. The specific structure of the bracket can have various forms, which is the prior art, and will not be repeated here.

In some specific embodiments, the water inlet porous section 5 is made of porous material, specifically, the material of the water inlet porous section 5 is ceramic or metal. The water inlet porous section 5 is fixedly embedded on the side wall of the monitoring container 4 . The way of fixing is the prior art, and will not be repeated here. Further, the metal can be made of stainless steel to prevent rust.

In some specific embodiments, the number and type of gas sensors 3 are determined according to the objectives of the monitoring work, and can monitor Rn, He, O ₂ , N ₂ , H ₂ , CO ₂ , NH ₃ , CH _4. Long-term real-time monitoring of the content changes of N ₂ O and other gases. Because the content of different gases will have significant differences, the accuracy of gas sensor 3 cannot be fully covered. Gas sensor 3 is only for preliminary monitoring of the content and percentage of each underground gas . When the monitoring data of the gas sensor 3 is abnormal, it is necessary to use the vacuum pump 13 to carry out fine sampling of the abnormal monitoring area, and to carry out detailed detection in the laboratory environment, and to know whether there is structural movement underground through the change of the gas content With chemical reaction, to know whether there is leakage of the sealed gas in the monitoring area, and to determine the leakage location and leakage amount according to the sampling point.

In some specific embodiments, an injection pipe 1 is also included, and the injection pipe 1 is inserted into the monitoring container 4 from the upper end of the monitoring container 4 . According to the monitored shallow underground formation and the apparent parameter information of the soil environment (such as permeability coefficient, water level, pH, gas content ratio, etc.), the modified gas can be injected into the monitoring container 4 through the injection pipe 1, and the monitoring area can be monitored. Modify the shallow soil environment. The injected gas is determined according to the underground environment and the required environment.

In some specific embodiments, the sampling pipe 7 and the injection pipe 1 are respectively sealed and connected to the upper part of the monitoring container 4 , and the closed structure of the monitoring container 4 can prevent other gases in the air from affecting soil gas monitoring and protect the gas sensor 3 .

In some specific embodiments, the connection between the sampling tube 7 and the monitoring container 4 is located at the upper end of the monitoring container 4 , that is, the sampling tube 7 is connected to the upper end of the monitoring container 4 . The gas sensor 3 is arranged on the upper end surface inside the monitoring container 4 and close to the connection between the sampling tube 7 and the monitoring container 4 .

In some specific embodiments, the differential pressure measuring device is a differential pressure flow meter.

In some specific embodiments, the differential pressure measuring device can also be a damper tube 8 , a one-way valve 10 and a differential pressure gauge 9 . The damping pipe 8 and the one-way valve 10 are connected between the monitoring container 4 and the constant volume container 11, the one-way valve 10 is connected between the damping pipe 8 and the constant volume container 11, and the differential pressure gauge 9 is connected in parallel to the damping pipe 8 through a branch pipe. On the sampling pipe 7 at the front and rear ends. By replacing the above-mentioned differential pressure flowmeter, the cost can be reduced.

Among them, the differential pressure gauge 9 is used to measure the pressure difference between the front and rear ends of the damping tube 8. As time goes by, the pressure difference on both sides of the damping tube 8 will automatically decay, and the permeability of the underground soil environment can be judged according to the decay curve of the differential pressure. .

One-way valve 10 is a standard one-way valve, and its direction is the fixed direction from underground soil to constant volume container 11, and one-way valve 10 can prevent the fluid in the external air from flowing back into the monitoring container 4 above the monitoring point soil to pollute it. The internal sample environment affects the specific values of each gas component and the pressure decay in the device, and setting the one-way valve 10 can increase the vacuuming effect of the vacuum pump 13 and the representativeness of collecting underground fluid samples.

The damping tube 8 is a capillary tube with fixed permeability, a porous tube, or is made of materials with fixed permeability coefficients such as various rock cores, which can increase the pressure decay time after the monitoring and sampling device is evacuated. The differential pressure on both sides of the damping tube 8 is monitored by the differential pressure gauge 9. When the permeability coefficient of the damping tube 8 is fixed, it can be judged according to the different pressure differential decay curves of the damping tube 8. The permeability of the underground soil environment, and inversion of the apparent characteristics and water level of the underground environment based on the gas sample analysis data.

In some specific embodiments, the sampling tube 7 is provided with a first control valve 12 for controlling the on-off of the sampling tube 7 . The first control valve 12 is arranged between the vacuum pump 13 and the constant volume container 11 . The sampling pipe 7 is used to collect fluid samples of the underground soil in the monitoring area, and to measure the permeability of the soil by connecting other components. When part of the gas sensor 3 is expensive or the service life is low, the gas sensor 3 can be supplemented by collecting soil samples by sampling, or the underground soil gas can be collected through the sampling pipe 7 when the measurement parameters of the gas sensor 3 are abnormally monitored, and the Soil gas samples are transported to relevant experimental equipment for further detailed testing.

In some specific embodiments, the injection pipe 1 is provided with a second control valve 2 for controlling the on-off of the injection pipe 1 .

Another embodiment of the present application proposes a method for monitoring and sampling soil gas components, using the above-mentioned monitoring and sampling device for soil gas components, including the following steps:

S1, arranging several monitoring sampling devices 16 at different monitoring positions in the monitoring area, initially monitoring data such as gas composition and content of the shallow soil at each monitoring position through the gas sensor 3, and observing whether the monitoring data at each monitoring position is abnormal;

S2, when the data monitored by the gas sensor 3 at a certain monitoring position is abnormal, or when it is necessary to know the soil atmosphere at a certain monitoring position, open the first control valve 12 and the vacuum pump 13 of the monitoring sampling device at the monitoring position, Sampling the soil gas at the monitoring position, pumping the soil gas into the constant volume container 11 for further experimental analysis, and judging the permeability of the soil environment through the monitoring data of the pressure difference measuring device, and obtaining the apparent permeability coefficient of the soil ;

S3, judging whether the soil in the monitoring area needs to be modified according to the experimental analysis data, when the soil in the monitoring area needs to be modified, determine the factors that need to be modified (such as soil pH), open the second control valve 2, and open the injection pipe 1 The modified gas is passed into the monitoring container 4 through the injection pipe 1, and the modified gas enters the soil outside the monitoring container 4 through the water inlet porous section 5 for modification, and the soil atmosphere is changed through reaction.

Moisture in the soil will enter the monitoring container 4 through the water inlet porous section 5, and be slowly discharged through the permeable membrane 6, so as to ensure that the monitoring and sampling device can still work normally in a waterlogged environment.

This application vacuumizes the monitoring sampling device during sampling. Due to the different permeability coefficients of the underground soil environment, a pressure difference will be formed inside the monitoring sampling device. The attenuation curve of the soil pressure difference is different for different permeability coefficients, and the underground soil can be fed back through the attenuation curve. For the permeability of the environment, the atmosphere and affinity of the soil can be understood through the gas sensor 3 and the content of each gas component in the sampling sample.

As shown in Fig. 2, in some specific embodiments, multiple monitoring and sampling devices 16 are arranged equidistantly in the monitoring area for matrix monitoring, and soil conditions and fluid samples can be obtained at multiple points in the monitoring area to accurately understand the characteristics of the fluid.

A plurality of monitoring sampling devices 16 are equidistantly arranged in the monitoring area, and the number thereof is determined according to the size of the monitoring area and monitoring requirements. The monitoring area is arranged in a matrix arrangement as shown in Figure 2, and the comprehensive parameters of underground fluid samples and soil gas can be obtained at multiple points and parameters. Through the monitoring data of multiple monitoring sampling devices 16, the detailed position of the abnormal point can be reversed, and the monitoring parameters of the matrix monitoring can be mixed and single-point sampling, and the corresponding monitoring parameters can be injected into the shallow underground soil in the monitoring area. The fluid transforms the atmosphere of the underground environment.

This application can realize relatively fine monitoring, and feed back the apparent data of shallow land and the underground soil environment such as water level, soil permeability, pH value and Rn, He, O ₂ , N ₂ , H ₂ , CO ₂ , NH ₃ , CH ₄ The content and proportion of gas substances such as N ₂ O and N 2 O are used to invert the apparent characteristics and geological movement status of the formation according to the monitoring value and geological modeling.

When the water level 15 is normal, the moisture and gas in the soil slowly enter the monitoring container 4 through the water inlet porous section 5 and the permeable membrane 6 until the sample environment inside the monitoring container 4 is consistent with the soil environment. When the water level 15 is too high, excess moisture enters the monitoring container 4 through the water inlet porous section 5, and is discharged to the soil 14 through the permeable membrane 6 on the bottom surface, so as to control the internal water level of the monitoring container 4, which can prevent waterlogging from affecting the monitoring. The protection device can work in the complex underground environment in the field for a long time.

The present application will be further elaborated below through specific examples.

Example 1

As shown in Figure 1, this embodiment proposes a monitoring and sampling device for soil gas components, including: a monitoring container 4, a gas sensor 3, a sampling tube 7, a damping tube 8, a differential pressure gauge 9, a one-way valve 10, a constant volume Container 11 , injection pipe 1 , first control valve 12 and second control valve 2 .

The monitoring container 4 is cylindrical, and the bottom of the monitoring container 4 is inserted into the soil 14. The lower end of the monitoring container 4 is provided with an opening, and a water-permeable membrane 6 is installed at a position above the opening in the monitoring container 4. The water-permeable membrane 6 is a two-way water-permeable membrane. The water-permeable membrane 6 is a hydrophilic material, and moisture can pass through the water-permeable membrane 6 normally. The water-permeable membrane 6 is installed in the monitoring container 4 through a bracket, and the bracket is arranged below the water-permeable membrane 6 . The function of the support is to support the permeable membrane 6, so that there is a certain space between the permeable membrane 6 and the soil, so as to prevent the permeable membrane 6 from being pierced by sand and gravel after the permeable membrane 6 contacts with the soil.

The middle section of the side wall of the monitoring container 4 is provided with a water inlet porous section 5, the water inlet porous section 5 is located above the water permeable membrane 6, the water inlet porous section 5 is made of stainless steel, and is embedded in the side of the monitoring container 4 in a fixed manner. on the wall. The gas sensor 3 is arranged in the monitoring container 4 , and the gas sensor 3 is located above the water inlet porous section 5 .

The opening of the lower part of the monitoring container 4 is directly connected with the ground soil 14, and the monitoring container 4 is covered above the monitoring point. When the water level 15 is normal, the moisture and gas in the soil slowly enter the monitoring container 4 through the water inlet porous section 5 and the permeable membrane 6 until the sample environment inside the monitoring container 4 is consistent with the soil environment. When the water level 15 is too high, excess moisture enters the monitoring container 4 through the water inlet porous section 5, and is discharged to the soil 14 through the permeable membrane 6 on the bottom surface, so as to control the internal water level of the monitoring container 4, which can prevent waterlogging from affecting the monitoring. The protection device can work in the complex underground environment in the field for a long time.

One end of the sampling tube 7 is connected to the upper end of the monitoring container 4 , and the other end of the sampling tube 7 is connected to the vacuum pump 13 . The gas sensor 3 is arranged on the upper end surface inside the monitoring container 4 and close to the connection between the sampling tube 7 and the monitoring container 4 . On the sampling pipe 7 between the monitoring container 4 and the vacuum pump 13, the damping pipe 8, the one-way valve 10, the constant volume container 11 and the first control valve 12 are sequentially connected, and the differential pressure gauge 9 is connected in parallel to the front and rear of the damping pipe 8 through branch pipes. On the sampling tube 7 at the end. Among them, the differential pressure gauge 9 is used to measure the pressure difference between the front and rear ends of the damping tube 8. As time goes by, the pressure difference on both sides of the damping tube 8 will automatically decay, and the permeability of the underground soil environment can be judged according to the decay curve of the differential pressure. . The one-way valve 10 is a standard one-way valve, and its direction is a fixed direction from the underground soil 14 to the constant volume container 11 .

The damping tube 8 can increase the time for pressure decay after the monitoring sampling device is evacuated, and a pressure difference is generated on both sides of the damping tube 8. When the permeability coefficient of the pipe 8 is fixed, the permeability of the underground soil environment can be judged according to the different pressure attenuation curves of the damping pipe 8, and the apparent characteristics and water level of the underground environment can be inverted according to the gas sample analysis data.

In this embodiment, in the soils of different environments whose water content is 15%, 35%, and 55% in experiments, the tested pressure differences P1, P2, and P3 have the relationship shown in Figure 3. According to the attenuation curve, Infer the apparent permeability coefficient k of the soil.

The injection pipe 1 is inserted into the monitoring container 4 from the upper end of the monitoring container 4 . According to the monitored shallow underground formation and the apparent parameter information of the soil environment (such as permeability coefficient, water level, pH, gas content ratio, etc.), the modified gas can be injected into the monitoring container 4 through the injection pipe 1, and the monitoring area can be monitored. Modify the shallow soil environment. The injected gas is determined according to the underground environment and the required environment.

The sampling pipe 7 and the injection pipe 1 are respectively sealed and connected to the upper part of the monitoring container 4 . The closed structure of the monitoring container 4 can prevent other gases in the air from affecting the soil gas monitoring and protect the gas sensor 3 .

This embodiment proposes a method for monitoring and sampling soil gas components, using the above-mentioned monitoring and sampling device for soil gas components, including the following steps:

S1, arranging several monitoring sampling devices 16 at different monitoring positions in the monitoring area, initially monitoring data such as gas composition and content of the shallow soil at each monitoring position through the gas sensor 3, and observing whether the monitoring data at each monitoring position is abnormal;

S2, when the data monitored by the gas sensor 3 at a certain monitoring position is abnormal, or when it is necessary to know the soil atmosphere at a certain monitoring position, open the first control valve 12 and the vacuum pump 13 of the monitoring sampling device at the monitoring position, Sampling the soil gas at the monitoring position, pumping the soil gas into the constant volume container 11 for further experimental analysis, and judging the permeability of the soil environment through the monitoring data of the pressure difference measuring device, and obtaining the apparent permeability coefficient of the soil ;

S3, judging whether the soil in the monitoring area needs to be modified according to the experimental analysis data, when the soil in the monitoring area needs to be modified, determine the factors that need to be modified (such as soil pH), open the second control valve 2, and open the injection pipe 1 The modified gas is passed into the monitoring container 4 through the injection pipe 1, and the modified gas enters the soil outside the monitoring container 4 through the water inlet porous section 5 for modification, and the soil atmosphere is changed through reaction.

Moisture in the soil 14 will enter the monitoring container 4 through the water inlet porous section 5, and be slowly discharged through the permeable membrane 6, so as to ensure that the monitoring and sampling device can still work normally in a waterlogged environment.

In this embodiment, the monitoring and sampling device is vacuumed during sampling. Due to the different permeability coefficients of the underground soil environment, a pressure difference will be formed inside the monitoring and sampling device. The attenuation curve of the soil pressure difference is different for different permeability coefficients. For the permeability of the soil environment, the soil atmosphere and affinity can be understood through the gas sensor 3 and the content of each gas component in the sampling sample.

Multiple monitoring and sampling devices 16 are equidistantly arranged in the monitoring area for matrix monitoring, and soil conditions and fluid samples can be obtained at multiple points in the monitoring area to accurately understand the characteristics of the fluid.

A plurality of monitoring sampling devices 16 are equidistantly arranged in the monitoring area, and the number thereof is determined according to the size of the monitoring area and monitoring requirements. The monitoring area is arranged in a matrix arrangement as shown in Figure 2, and the comprehensive parameters of underground fluid samples and soil gas can be obtained at multiple points and parameters. Through the monitoring data of multiple monitoring and sampling devices 16, the detailed position of the abnormal point can be reversed, and the monitoring parameters of matrix monitoring can be mixed and single-point sampled, and the abnormal single-point information can be quickly measured through the dichotomy method, which can deal with various Monitoring and sampling tasks of various underground environments. Through the monitoring parameters, the corresponding fluid can be injected into the shallow underground soil in the monitoring area to transform the underground environment.

This embodiment can realize relatively fine monitoring, and feed back the apparent data of shallow land and the underground soil environment such as water level, soil permeability, pH value and Rn, He, O ₂ , N ₂ , H ₂ , CO ₂ , NH ₃ , CH _4. The content and proportion of N ₂ O and other gas substances are used to invert the apparent characteristics and geological movement of the formation according to the monitoring value and geological modeling.

In describing the present invention, it should be understood that the terms "center", "longitudinal", "transverse", "length", "width", "thickness", "upper", "lower", "front", " Back", "Left", "Right", "Vertical", "Horizontal", "Top", "Bottom", "Inner", "Outer", "Clockwise", "Counterclockwise", "Axial", The orientation or positional relationship indicated by "radial", "circumferential", etc. is based on the orientation or positional relationship shown in the drawings, and is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying the referred device or element Must be in a particular orientation, be constructed in a particular orientation, and operate in a particular orientation, and therefore should not be construed as limiting the invention.

In addition, the terms "first" and "second" are used for descriptive purposes only, and cannot be interpreted as indicating or implying relative importance or implicitly specifying the quantity of indicated technical features. Thus, the features defined as "first" and "second" may explicitly or implicitly include at least one of these features. In the description of the present invention, "plurality" means at least two, such as two, three, etc., unless otherwise specifically defined.

In the present invention, unless otherwise clearly specified and limited, terms such as "installation", "connection", "connection" and "fixation" should be understood in a broad sense, for example, it can be a fixed connection or a detachable connection , or integrated; can be mechanically connected, can also be electrically connected or can communicate with each other; can be directly connected, can also be indirectly connected through an intermediary, can be the internal communication of two components or the interaction relationship between two components, Unless expressly defined otherwise. Those of ordinary skill in the art can understand the specific meanings of the above terms in the present invention according to specific situations.

In the present invention, unless otherwise clearly specified and limited, the first feature may be in direct contact with the first feature or the first and second feature may be in direct contact with the second feature through an intermediary. touch. Moreover, "above", "above" and "above" the first feature on the second feature may mean that the first feature is directly above or obliquely above the second feature, or simply means that the first feature is higher in level than the second feature. "Below", "beneath" and "beneath" the first feature may mean that the first feature is directly below or obliquely below the second feature, or simply means that the first feature is less horizontally than the second feature.

As used herein, the terms "one embodiment," "some embodiments," "example," "specific examples," or "some examples" mean specific features, structures, materials, or features described in connection with the embodiment or example. A feature is included in at least one embodiment or example of the invention. In this specification, the schematic representations of the above terms are not necessarily directed to the same embodiment or example. Furthermore, the described specific features, structures, materials or characteristics may be combined in any suitable manner in any one or more embodiments or examples. In addition, those skilled in the art can combine and combine different embodiments or examples and features of different embodiments or examples described in this specification without conflicting with each other.

Although the embodiments of the present invention have been shown and described above, it can be understood that the above embodiments are exemplary and should not be construed as limiting the present invention, and those skilled in the art can make the above-mentioned The embodiments are subject to changes, modifications, substitutions and variations.

Claims (10)

1. A soil gas composition monitoring and sampling device, comprising:

the monitoring container is inserted into soil, an opening is formed in the lower end of the monitoring container, a water permeable device is arranged above the opening in the monitoring container, a water inlet porous section is arranged on the side wall of the monitoring container and above the water permeable device, a gas sensor is arranged in the monitoring container and above the water inlet porous section;

the sampling tube, the monitoring container is connected to the one end of sampling tube, and the vacuum pump is connected to the other end of sampling tube, is connected with pressure differential measuring device and constant volume container on the sampling tube between monitoring container and vacuum pump, and the constant volume container is connected between pressure differential measuring device and vacuum pump.

2. A soil gas composition monitoring and sampling device according to claim 1, wherein the water permeable means is a water permeable membrane.

3. A soil gas composition monitoring and sampling device as claimed in claim 2, wherein the water permeable membrane is mounted in the monitoring vessel by means of a bracket, the bracket being disposed below the water permeable membrane.

4. The soil gas composition monitoring and sampling device of claim 1, wherein the porous section of the inlet water is made of ceramic or metal.

5. The soil gas composition monitoring and sampling device as claimed in claim 1, further comprising an injection tube inserted into the monitoring vessel.

6. The soil gas composition monitoring and sampling device as claimed in claim 5, wherein the sampling tube and the injection tube are respectively connected with the upper part of the monitoring container in a sealing way.

7. The soil gas composition monitoring and sampling device according to claim 1, wherein the differential pressure measuring device comprises a damping tube, a one-way valve and a differential pressure gauge for measuring the differential pressure at the front end and the rear end of the damping tube, the damping tube and the one-way valve are connected between the monitoring container and the constant volume container, the one-way valve is connected between the damping tube and the constant volume container, and the differential pressure gauge is connected in parallel to the sampling tubes at the front end and the rear end of the damping tube through a branch tube.

8. The soil gas composition monitoring and sampling device of claim 1, wherein said differential pressure measuring device is a differential pressure flow meter.

9. A soil gas composition monitoring and sampling method, characterized in that, the soil gas composition monitoring and sampling device of any one of claims 1-8 is used, comprising the following steps:

s1, arranging a plurality of monitoring sampling devices at different monitoring positions in a monitoring area, primarily monitoring the soil gas components and content of each monitoring position through a gas sensor, and observing whether monitoring data are abnormal or not;

s2, when data monitored by a gas sensor at a certain monitoring position is abnormal, starting a first control valve and a vacuum pump of a monitoring sampling device at the monitoring position, sampling the soil gas at the monitoring position, pumping the soil gas into a constant volume container for further experimental analysis, and judging the permeability of the soil environment through the monitoring data of a differential pressure measuring device;

and S3, judging whether the soil in the monitoring area needs to be modified according to experimental analysis data, determining the factor needing to be modified when the soil in the monitoring area needs to be modified, opening the injection pipe, introducing modified gas into the monitoring container through the injection pipe, and modifying the modified gas into the soil outside the monitoring container through the water inlet porous section.

10. The soil gas composition monitoring and sampling method according to claim 9, wherein a plurality of the monitoring and sampling devices are arranged in a matrix in the monitoring area.

Images