A well arrangement method and system of an underground gasification hydrologic monitoring well

Abstract

This invention discloses a method and system for the placement of underground gasification hydrological monitoring wells, relating to the technical field of underground coal gasification processes and subsequent hydrological monitoring well placement. The method includes: dividing the gasification zone into multiple concentric circles based on the concentric circle theory; establishing a mathematical model of pollutant concentration and migration distance based on indoor simulation experiments to determine the radii of the multiple concentric circles; and arranging hydrological monitoring wells within the multiple concentric circles according to the water flow direction. This invention, based on the concentric circle principle, divides the gasification zone into three concentric circles—a production area, a monitoring area, and a compliance area—for tiered monitoring. This allows for timely and effective pollutant monitoring, timely and effective assessment of the surrounding environment, and provision of reasonable solutions based on potential pollution situations to promptly prevent pollution. Simultaneously, it can quantitatively study the relationship between pollutant concentration and migration distance, determine the distance between each concentric circle, and effectively guide the on-site well placement.

Description

Technical Field

[0001] This invention relates to the field of underground coal gasification process and subsequent hydrological monitoring well placement technology, and particularly to a method and system for placing underground gasification hydrological monitoring wells. Background Technology

[0002] Underground coal gasification is a revolutionary technology for the clean utilization of coal. It involves constructing an "underground gasifier" within the original coal seam to convert coal in situ into clean energy sources such as methane, hydrogen, and carbon monoxide. Simultaneously, the generated carbon dioxide is backfilled into underground cavities and saline aquifers, resulting in no carbon dioxide or pollutant emissions. While currently primarily targeting medium-deep coal seams, reducing the risk of drinking water pollution and surface subsidence compared to shallower seams, the impact of underground gasification on groundwater remains a significant concern, and specific operational standards are currently lacking. Developing a guiding system for the placement of underground gasification monitoring wells would provide reliable and comprehensive basic data for understanding the subsequent impacts of underground gasification on the groundwater environment.

[0003] Patent CN103696752B provides a "method for controlling pollutants from underground gasification," comprising the following steps: (S1) determining the distribution coefficient of pollutants in the underground gasification zone, the gasification pressure of the underground gasification zone, the concentration difference of pollutants in the study area obtained by monitoring through observation wells, and the distance of the observation wells from the underground gasification zone; (S2) establishing a functional relationship between the migration rate of underground gasification pollutants and the underground gasification pressure based on all the physical quantities determined above; (S3) obtaining the critical gasification pressure by using the critical migration rate of pollutants as the input value of the function; (S4) keeping the diffusion range of pollutants within a specified range outside the underground gasification zone by ensuring that the gasification pressure of the underground gasification zone does not exceed the critical gasification pressure. Currently, there are few dedicated hydrological monitoring wells for underground gasification. This invention utilizes existing gasification wells to periodically sample and monitor water quality changes, which can only monitor the degree of pollution in the gasification zone but cannot determine the migration distance and range of pollutants, nor can it determine whether there is pollution in the surrounding strata.

[0004] Chen Yawei et al. published an article entitled “Evaluation of the Impact of Coal Underground Gasification on Groundwater Quality and Trend Analysis” in the Journal of the University of Chinese Academy of Sciences (2015, 32(03): 309-316). The article introduced that, based on experience, several observation wells were drilled at different distances near the gasification zone. Although the possible pollution range near the gasification zone or the existence of pollution in the surrounding area could be monitored, the distribution of specific pollutants was still lacking.

[0005] Therefore, providing a scientific well placement method for groundwater monitoring wells, which can efficiently monitor underground gasification zones, thereby improving the accuracy and reliability of data acquisition and timely treatment of pollution, is an important problem that urgently needs to be solved. Summary of the Invention

[0006] The purpose of this invention is to provide a method and system for the placement of monitoring wells for underground gasification hydrology. It proposes a scientific well placement method for monitoring underground hydrology based on current underground gasification technology. This well placement method implements hierarchical monitoring according to a concentric structure, dividing the area into production zones, monitoring zones, and compliance zones. Furthermore, it proposes a method for calculating the distance between monitoring wells for each zone. According to the technology provided by this invention, by implementing well placement at different levels, the underground gasification zone can be monitored efficiently, improving the accuracy and reliability of data acquisition and enabling timely remediation of pollution. To achieve the above objectives, this invention provides the following technical solution: On one hand, the present invention provides a method for the placement of underground gasification hydrological monitoring wells, the method comprising the following steps: According to the theory of layered structure, multiple layers are divided with the gasification zone as the center. A mathematical model of pollutant concentration and migration distance was established based on indoor simulation experiments to determine the radii of the multiple concentric circles; Hydrological monitoring wells are arranged in the multiple concentric circles according to the direction of water flow.

[0007] Furthermore, the method also includes the following steps: Identify the target coal seam within the risk strata; The target coal seam was subjected to petrographic and mineral composition analysis to determine the components of pollutants; Based on the pollutant composition, the pollution category is identified, and the gasification zone is determined.

[0008] Furthermore, the multiple concentric circles include: a production area, a monitoring area, and a compliance area.

[0009] Furthermore, the mathematical model established based on indoor simulation experiments to determine the radii of the multiple concentric circles includes: A mathematical model of pollutant concentration and migration distance was established based on indoor simulation experiments, and a curve of pollutant concentration and migration distance in the study area was plotted. Based on the graph, the radius of the production area and the radius of the monitoring area are determined.

[0010] Furthermore, the mathematical model for the relationship between pollutant concentration and migration distance is expressed as follows: ; In the formula: C represents the concentration of the pollutant at a certain time and distance, with the unit being mg / cm³. 3 C0 represents the pollutant concentration at the gasification well, in mg / cm³. 3 ;erfc represents the complementary error function; exp represents the exponential function with base e; D0 represents the dispersion coefficient, in m. 2 / s; X represents distance in meters; T represents time in seconds; U0 represents groundwater flow velocity in meters per second; λ represents a comprehensive coefficient considering decay, adsorption, and biodegradation in 1 / s.

[0011] Furthermore, the radius of the production area is the distance corresponding to the inflection point a of the attenuation in the curve graph; The radius of the monitoring area is the distance corresponding to the safe concentration point b in the curve.

[0012] Furthermore, the arrangement of hydrological monitoring wells within the multiple concentric layers according to the water flow direction includes: Based on the direction of water flow, a first hydrological monitoring well is arranged above the water flow as a reference well; a second hydrological monitoring well is arranged in the production area in conjunction with the gasification well; a third hydrological monitoring well is arranged on the outermost side of the production area; a fourth hydrological monitoring well is arranged directly below the downstream direction of the monitoring area; a fifth and a sixth hydrological monitoring well are arranged on the left and right sides respectively; and a seventh hydrological monitoring well is arranged in the compliance area, ensuring that hydrological monitoring wells are arranged in all the aforementioned concentric circles.

[0013] On the other hand, the present invention also provides a well layout system for underground gasification hydrological monitoring wells, the system comprising: a division unit, a first determination unit, and an arrangement unit; wherein, The division unit is used to divide the gasification zone into multiple layers based on the layer structure theory. The first determining unit is used to establish a mathematical model of pollutant concentration and migration distance based on indoor simulation experiments, and to determine the radius of the multiple concentric circles; The arrangement unit is used to arrange hydrological monitoring wells in the multiple concentric circles according to the direction of water flow.

[0014] Furthermore, the system further includes: a discrimination unit, a second determination unit, and a third determination unit; wherein, The discrimination unit is used to identify target coal seams within risk zones. The second determining unit is used to perform coal petrography and mineral composition analysis on the target coal seam to determine the pollutant composition. The third determining unit is used to identify the pollution category and determine the gasification zone based on the pollutant composition.

[0015] Further, the first determining unit includes: a drawing module and a determining module; wherein, The plotting module is used to establish a mathematical model of pollutant concentration and migration distance based on indoor simulation experiments, and to plot the curves of pollutant concentration and migration distance in the study area. The determination module is used to determine the radius of the production area and the radius of the monitoring area based on the curve graph.

[0016] Furthermore, the arrangement unit is specifically used for, Based on the direction of water flow, a first hydrological monitoring well is arranged above the water flow as a reference well; a second hydrological monitoring well is arranged in the production area in conjunction with the gasification well; a third hydrological monitoring well is arranged on the outermost side of the production area; a fourth hydrological monitoring well is arranged directly below the downstream direction of the monitoring area; a fifth and a sixth hydrological monitoring well are arranged on the left and right sides respectively; and a seventh hydrological monitoring well is arranged in the compliance area, ensuring that hydrological monitoring wells are arranged in all the aforementioned concentric circles.

[0017] The technical effects and advantages of this invention are as follows: First, this invention divides the gasification zone into three concentric zones—the production zone, the monitoring zone, and the compliance zone—based on the principle of a concentric structure. This hierarchical monitoring enables timely and effective monitoring of pollutants and timely and effective assessment of the surrounding environment. Second, this invention quantitatively studies the relationship between pollutant concentration and migration distance in the research area, which can determine the distance of each sphere and effectively guide the layout of well sites on site. Third, the tiered monitoring system of this invention can monitor pollutants in a timely and effective manner, provide reasonable solutions based on potential pollution situations, and promptly prevent pollution.

[0018] Other features and advantages of the invention will be set forth in the following description, and will be apparent in part from the description, or may be learned by practicing the invention. The objects and other advantages of the invention may be realized and obtained by means of the structures pointed out in the description and the drawings. Attached Figure Description

[0019] Figure 1 This is a flowchart of a method for placing underground gasification hydrological monitoring wells according to the present invention; Figure 2 This is a graph showing the determination of the gasification zone radius in an embodiment of the present invention. Figure 3 This is a schematic diagram of the gasification hydrological monitoring well ring layout according to an embodiment of the present invention; In the diagram, 1 is the first hydrological monitoring well (reference well); 2 is the gasification well; 3 is the second hydrological monitoring well; 4 is the third hydrological monitoring well; 5 is the fourth hydrological monitoring well; 6 is the fifth hydrological monitoring well; 7 is the sixth hydrological monitoring well; and 8 is the seventh hydrological monitoring well. Detailed Implementation

[0020] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0021] To address the shortcomings of existing technologies, this invention discloses a method for the placement of underground gasification hydrological monitoring wells. Figure 1 This is a flowchart of a method for placing underground gasification hydrological monitoring wells according to the present invention, as shown below. Figure 1 As shown, the method includes the following steps: S1. Identify the target coal seam within the risk stratum; S2. Perform coal petrography, coal quality and mineral composition analysis on the target coal seam to determine the components of pollutants; S3. Based on the pollutant composition, identify the pollution category and determine the gasification zone.

[0022] S4. According to the theory of layered structure, multiple layers are divided with the gasification zone as the center; S5. Establish a mathematical model of pollutant concentration and migration distance based on indoor simulation experiments, and determine the radii of the multiple concentric circles; S6. Based on the direction of water flow, arrange hydrological monitoring wells within the multiple concentric circles.

[0023] In step S1 of the present invention, by collecting hydrogeological data of the study area, the aquifers adjacent to the coal seam and the flow direction of the corresponding groundwater are clarified, and the target coal seam in the risk stratum is preliminarily identified.

[0024] In step S2 of the present invention, the target coal seam in step S1 is subjected to coal petrographic analysis and mineral composition analysis to identify possible pollutant components.

[0025] In step S3 of the present invention, the pollutants include organic and inorganic components, the main pollution categories are identified, and the gasification zone is determined.

[0026] In step S4 of this invention, based on the principle of a concentric structure, the gasification zone is divided into three concentric zones: a production zone, a monitoring zone, and a compliance zone, for hierarchical monitoring. The production zone refers to the main gasification operation area; the monitoring zone is a warning buffer zone that monitors significant changes in warning indicators; and the compliance zone refers to areas expected to be unaffected by underground coal gasification operations, meeting the requirements of environmental management departments.

[0027] In step S5 of this invention, a mathematical model of pollutant concentration and migration distance is established based on indoor simulation experiments to determine the radii of the multiple concentric circles, including: A mathematical model of pollutant concentration and migration distance was established based on indoor simulation experiments, and a curve of pollutant concentration and migration distance in the study area was plotted. Based on the graph, the radius of the production area and the radius of the monitoring area are determined.

[0028] Since the migration of pollutants in groundwater is mainly affected by groundwater convection, molecular diffusion, dispersion, adsorption and desorption in solid and liquid phases, radioactive decay, biodegradation, and adsorption retention, this patent establishes a mathematical model for the transformation of organic pollution in the groundwater environment based on a comprehensive consideration of the above effects. Specifically, the mathematical model for the relationship between pollutant concentration and migration distance is expressed as follows: ; In the formula: C represents the concentration of the pollutant at a certain time and distance, with the unit being mg / cm³. 3 C0 represents the pollutant concentration at the gasification well, in mg / cm³. 3 ;erfc represents the complementary error function; exp represents the exponential function with base e; D0 represents the dispersion coefficient, in m. 2 / s; X represents distance in meters; T represents time in seconds; U0 represents groundwater flow velocity in meters per second; λ represents a comprehensive coefficient considering decay, adsorption, and biodegradation in 1 / s.

[0029] Furthermore, the radius of the production area is the distance corresponding to the inflection point a of the attenuation in the curve; the radius of the monitoring area is the distance corresponding to the safe concentration point b in the curve.

[0030] In step S6 of the present invention, arranging hydrological monitoring wells within the plurality of concentric layers according to the water flow direction includes: Based on the direction of water flow, a first hydrological monitoring well is arranged above the water flow as a reference well; a second hydrological monitoring well is arranged in the production area in conjunction with the gasification well; a third hydrological monitoring well is arranged on the outermost side of the production area; a fourth hydrological monitoring well is arranged directly below the downstream direction of the monitoring area; a fifth and a sixth hydrological monitoring well are arranged on the left and right sides respectively; and a seventh hydrological monitoring well is arranged in the compliance area, ensuring that hydrological monitoring wells are arranged in all the aforementioned concentric circles.

[0031] It should be noted that a dynamic layout principle is adopted in the gasification monitoring process, with wells arranged sequentially in the production area, monitoring area, and compliance area, and the distance between wells can be adjusted according to the degree of pollutants.

[0032] Taking a gasification research area in Northwest China as an example, before well placement in the gasification zone, hydrogeological data showed that the groundwater flow was from northeast to southwest, and the main pollutant was phenol. Based on the geological and hydrological parameters of the area, a mathematical model was used to plot the relationship between pollutant concentration and migration distance in the research area. Figure 2 This is a curve diagram for determining the radius of the gasification zone in an embodiment of the present invention, as shown below. Figure 2As shown, based on the curve attenuation, the inflection point a is found to be 80m and the inflection point b is 500m. Thus, the radius of the production area is determined to be 80m, the radius of the monitoring area is 500m, and the area beyond 500m is the compliance area. In this way, the three concentric circles of the production area, monitoring area, and compliance area are quantitatively drawn, which can be used for hierarchical monitoring in the later stage. Figure 3 This is a schematic diagram of the gasification hydrological monitoring well layer layout according to an embodiment of the present invention, as shown below. Figure 3 As shown, in the specific deployment of well locations, according to the present invention, taking into account the direction of water flow, a first hydrological monitoring well (well 1) is arranged above the water flow as a reference well; a second hydrological monitoring well (well 3) is arranged in the production area in conjunction with the gasification well (well 2); a third hydrological monitoring well (well 4) is arranged on the outermost side of the production area; a fourth hydrological monitoring well (well 5) is arranged directly below the downstream direction of the monitoring area; a fifth hydrological monitoring well (well 6) and a sixth hydrological monitoring well (well 7) are arranged on the left and right sides respectively; and a seventh hydrological monitoring well (well 8) is arranged in the compliance area, ensuring that hydrological monitoring wells are arranged in all the multiple concentric circles.

[0033] Based on the above method, the present invention also discloses a well placement system for underground gasification hydrological monitoring wells, the system comprising: a discrimination unit, a first determination unit, a second determination unit, a division unit, a third determination unit, and a placement unit; wherein, The discrimination unit is used to identify target coal seams within risk zones. The first determining unit is used to perform coal petrography and mineral composition analysis on the target coal seam to determine the pollutant composition. The second determining unit is used to identify the pollution category and determine the gasification zone based on the pollutant composition.

[0034] The division unit is used to divide the gasification zone into multiple layers based on the layer structure theory. The third determining unit is used to establish a mathematical model of pollutant concentration and migration distance based on indoor simulation experiments, and to determine the radius of the multiple concentric circles; The arrangement unit is used to arrange monitoring wells within the multiple concentric layers according to the direction of water flow.

[0035] Further, the first determining unit includes: a drawing module and a determining module; wherein, The plotting module is used to establish a mathematical model of pollutant concentration and migration distance based on indoor simulation experiments, and to plot the curves of pollutant concentration and migration distance in the study area. The determination module is used to determine the radius of the production area and the radius of the monitoring area based on the curve graph.

[0036] Furthermore, in the division unit, the multiple concentric circles include: a production area, a monitoring area, and a compliance area.

[0037] Furthermore, in the third determining unit, the mathematical model expression for the pollutant concentration and migration distance is: ; In the formula: C represents the concentration of the pollutant at a certain time and distance, with the unit being mg / cm³. 3 C0 represents the pollutant concentration at the gasification well, in mg / cm³. 3 ;erfc represents the complementary error function; exp represents the exponential function with base e; D0 represents the dispersion coefficient, in m. 2 / s; X represents distance in meters; T represents time in seconds; U0 represents groundwater flow velocity in meters per second; λ represents a comprehensive coefficient considering decay, adsorption, and biodegradation in 1 / s.

[0038] Furthermore, the arrangement unit is specifically used for, Based on the direction of water flow, a first hydrological monitoring well is arranged above the water flow as a reference well; a second hydrological monitoring well is arranged in the production area in conjunction with the gasification well; a third hydrological monitoring well is arranged on the outermost side of the production area; a fourth hydrological monitoring well is arranged directly below the downstream direction of the monitoring area; a fifth and a sixth hydrological monitoring well are arranged on the left and right sides respectively; and a seventh hydrological monitoring well is arranged in the compliance area, ensuring that hydrological monitoring wells are arranged in all the aforementioned concentric circles.

[0039] Finally, it should be noted that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for deploying underground gasification hydrological monitoring wells, characterized in that, The method includes the following steps: According to the theory of layered structure, multiple layers are divided with the gasification zone as the center. A mathematical model of pollutant concentration and migration distance was established based on indoor simulation experiments to determine the radii of the multiple concentric circles; Hydrological monitoring wells are arranged in the multiple concentric circles according to the direction of water flow. The multiple concentric zones include: a production zone, a monitoring zone, and a compliance zone; The aforementioned mathematical model establishing pollutant concentration and migration distance based on indoor simulation experiments, and determining the radii of the multiple concentric circles, includes: A mathematical model of pollutant concentration and migration distance was established based on indoor simulation experiments, and a curve of pollutant concentration and migration distance in the study area was plotted. Based on the graph, determine the radius of the production area and the radius of the monitoring area; The mathematical model for the relationship between pollutant concentration and migration distance is expressed as follows: ； In the formula: C represents the concentration of the pollutant at a certain time and distance, with the unit being mg / cm³. 3 C0 represents the pollutant concentration at the gasification well, in mg / cm³. 3 ;erfc represents the complementary error function; exp represents the exponential function with base e; D0 represents the dispersion coefficient, in m. 2 / s; X represents distance in meters; T represents time in seconds; U0 represents groundwater flow velocity in meters per second; λ represents a comprehensive coefficient considering decay, adsorption, and biodegradation in 1 / s.

2. The well placement method for underground gasification hydrological monitoring wells according to claim 1, characterized in that, The method further includes the following steps: Identify the target coal seam within the risk strata; The target coal seam was subjected to petrographic and mineral composition analysis to determine the components of pollutants; Based on the pollutant composition, the pollution category is identified, and the gasification zone is determined.

3. The well placement method for underground gasification hydrological monitoring wells according to claim 1, characterized in that, The arrangement of hydrological monitoring wells within the multiple concentric layers according to the water flow direction includes: Based on the direction of water flow, a first hydrological monitoring well is arranged above the water flow as a reference well; a second hydrological monitoring well is arranged in the production area in conjunction with the gasification well; a third hydrological monitoring well is arranged on the outermost side of the production area; a fourth hydrological monitoring well is arranged directly below the downstream direction of the monitoring area; a fifth and a sixth hydrological monitoring well are arranged on the left and right sides respectively; and a seventh hydrological monitoring well is arranged in the compliance area, ensuring that hydrological monitoring wells are arranged in all the aforementioned concentric circles.

4. A well placement system for underground gasification hydrological monitoring wells, characterized in that, The system includes: a partitioning unit, a first determining unit, and an arrangement unit; wherein... The division unit is used to divide the gasification zone into multiple layers based on the layer structure theory. The first determining unit is used to establish a mathematical model of pollutant concentration and migration distance based on indoor simulation experiments, and to determine the radius of the multiple concentric circles; An arrangement unit is used to arrange hydrological monitoring wells within the multiple concentric layers according to the direction of water flow. The division unit includes multiple concentric circles: a production area, a monitoring area, and a compliance area; The first determining unit includes: a drawing module and a determining module; wherein, The plotting module is used to establish a mathematical model of pollutant concentration and migration distance based on indoor simulation experiments, and to plot the curves of pollutant concentration and migration distance in the study area. The determination module is used to determine the radius of the production area and the radius of the monitoring area based on the curve graph; The mathematical model for the relationship between pollutant concentration and migration distance is expressed as follows: ； In the formula: C represents the concentration of the pollutant at a certain time and distance, with the unit being mg / cm³. 3 C0 represents the pollutant concentration at the gasification well, in mg / cm³. 3 ;erfc represents the complementary error function; exp represents the exponential function with base e; D0 represents the dispersion coefficient, in m. 2 / s; X represents distance in meters; T represents time in seconds; U0 represents groundwater flow velocity in meters per second; λ represents a comprehensive coefficient considering decay, adsorption, and biodegradation in 1 / s.

5. The well placement system for underground gasification hydrological monitoring wells according to claim 4, characterized in that, The system further includes: a discrimination unit, a second determination unit, and a third determination unit; wherein... The discrimination unit is used to identify target coal seams within risk zones. The second determining unit is used to perform coal petrography and mineral composition analysis on the target coal seam to determine the pollutant composition. The third determining unit is used to identify the pollution category and determine the gasification zone based on the pollutant composition.

6. The well placement system for underground gasification hydrological monitoring wells according to claim 4, characterized in that, The arrangement unit is specifically used for, Based on the direction of water flow, a first hydrological monitoring well is arranged above the water flow as a reference well; a second hydrological monitoring well is arranged in the production area in conjunction with the gasification well; a third hydrological monitoring well is arranged on the outermost side of the production area; a fourth hydrological monitoring well is arranged directly below the downstream direction of the monitoring area; a fifth and a sixth hydrological monitoring well are arranged on the left and right sides respectively; and a seventh hydrological monitoring well is arranged in the compliance area, ensuring that hydrological monitoring wells are arranged in all the aforementioned concentric circles.

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