A borehole distribution method suitable for hydrogeological modeling requirements

Abstract

The present application relates to a kind of drilling point distribution method suitable for hydrogeological modeling needs, first according to the area size of modeling area selection point distribution scheme, then the modeling site is generalized as simple rectangular site, according to the length-width ratio of rectangle is calculated in different cases, then according to the height difference of modeling site, the length of rectangular small side, and increase confidence interval, point distribution interval is calculated using mathematical formula, combined with existing drilling point and slope condition, obtain the final point distribution scheme.The problem that there is no unified point distribution method for the stratum drilling required in modeling is solved, at the same time, the area and height difference of modeling area are combined, so that the point distribution method is more specific, the overall point distribution quantity is not large after calculation, which can meet the accurate and economic requirements of modeling, and does not need too much pre-research, saving manpower and material resources.

Description

Technical Field

[0001] This invention belongs to the field of hydrogeology, and in particular relates to a borehole layout method suitable for hydrogeological modeling needs when hydrogeological modeling of a modeling site is required and the accuracy of stratigraphic distribution and thickness variation in the model is highly demanding. Background Technology

[0002] Hydrogeological modeling is currently an effective method for studying groundwater and soil pollution. It can form a model by initially depicting groundwater conditions and generalizing recharge, runoff, and drainage conditions such as rainfall. By changing pollutant parameters, it can predict the spatial and temporal variations of pollutants, providing fundamental data for soil and groundwater pollution remediation. Therefore, a highly accurate hydrogeological model is a prerequisite for soil and groundwater pollution remediation, while a relatively accurate description of stratigraphic conditions is the foundation for establishing such a model.

[0003] Hydrogeological modeling studies of groundwater and soil pollution require drilling operations, which are often expensive and cause significant disturbance. Improper post-drilling treatment can also lead to the injection of new pollution. Therefore, obtaining the most accurate subsurface stratigraphic distribution with the least amount of drilling data is crucial. The modeling area often includes not only the target site area but also regions within the same basic hydrological unit to ensure the independence of the hydrological cycle in that area. Therefore, the area is often large. A small number of boreholes may not be sufficient for accurate stratigraphic interpolation, while an excessive number of boreholes can lead to excessive costs and the risk of introducing secondary pollution. Thus, the arrangement of boreholes is critical. Currently, my country has publicly available "National Important Borehole Data Platforms" with a large amount of borehole data, which can serve as an effective source of borehole data, effectively complementing self-drilled data and further saving costs. However, in practice, it has been found that borehole data platforms cannot meet the modeling requirements, and actual self-drilling is often indispensable.

[0004] Considering the economics and practicality of drilling, the primary direct factor influencing the number of boreholes is the area of ​​the modeling region. Secondly, the slope (elevation difference) of the entire modeling region is also crucial in affecting the number of boreholes. It is generally believed that the distribution of strata, i.e., the elevation of the top and bottom plates, roughly follows the trend of topographic changes. In areas with large elevation changes, the top and bottom plate elevations of the strata often vary significantly, and drastic changes in stratum thickness, even pinch-out, are likely to occur. Therefore, key points with large slope variations should be given sufficient attention, as the strata are likely to undergo significant changes. Simply increasing the area of ​​the region by the number of boreholes can easily lead to an excessive number of boreholes and significant economic pressure. The slopes of different modeling regions vary considerably, and proportionally increasing the number of boreholes will also result in redundant boreholes. Therefore, an effective borehole placement method is needed to provide guidance for borehole placement in hydrogeological modeling.

[0005] Current research on soil sampling methods mainly focuses on contaminated site investigation methods, and there are many mature documents in this area. However, there is little coverage of borehole sampling methods required for hydrogeological modeling. The "Specification for Soil and Groundwater Investigation and Risk Assessment of Contaminated Sites" (DD2014-06) provides methods for the layout of investigation points in surface soil surveys. It first classifies the site's contamination status and provides corresponding methods. The spacing is determined based on the pollution source investigation, providing a corresponding sampling spacing table and calculation formula. If the preconditions are not met, the spacing is determined using 1 / 10 to 1 / 20 of the site's side length, and the calculation method for sampling spacing is clearly defined. However, this method is only suitable for surface sampling, which is relatively simple and cost-effective, and involves relatively dense sampling. Since it is based on pollution source investigation, it is relatively unsuitable for borehole sampling, which is more expensive and lacks sufficient preliminary research results. The "Technical Regulations for Non-Sampling of Suspected Contaminated Sites in Key Industry Enterprises' Land Use Survey" (Trial) clearly marks the locations of sampling points in suspected contaminated areas, such as underground tanks and pipelines, and sets requirements for sampling depth and quantity. Sampling depths are often less than 3 meters, therefore, it cannot provide a reference for borehole sampling. Furthermore, the entire process focuses on the suspected contaminated area and does not involve the surrounding area, which is relatively small. The "Technical Guidelines for Risk Control and Remediation Monitoring of Soil Pollution in Construction Land" (HJ25.2-2019) stipulates some general sampling requirements, requiring that the representative area of ​​the monitoring points after remediation should not exceed a certain area value. For example, the representative area of ​​monitoring points for hazardous waste soil should not exceed 100 m². 2 The requirements differ slightly from the previous two. While specifying that the method of borehole placement is not affected, only the upper limit is defined, providing some reference value but not direct guidance for borehole placement. The "Guidelines for Generalization of Hydrogeological Models," directly related to hydrogeological models, only specifies the modeling process and commonly used generalization methods, such as how to generalize head boundaries and what geological data is required. However, it does not clarify how to collect borehole data in a way that is both economical and ensures a certain level of accuracy; this aspect remains a blank in the standard documents.

[0006] Regarding patent articles, most focus on sampling point layout methods for contaminated sites. CN108507813A discloses a typical soil and groundwater sampling method for petroleum hydrocarbon contaminated sites, which involves multiple soil samplings in the contaminated area. First, samples are collected from the plant area, then soil and groundwater samples are collected, and finally, denser sampling is performed. However, this method still does not involve high-depth sampling and does not provide a detailed description of the point layout method. CN110457422A discloses an automatic soil sample collection point layout system and method, which uses a three-dimensional vector model of the soil to divide the soil and a point quantity setting subsystem to directly generate point layout rules and point quantity, resulting in more accurate soil point layout. However, it does not explain the accuracy of the point layout or mention the specific number of points, making it less reliable for reference. CN11707490A discloses a method for phased and zoned sampling in agricultural land soil pollution investigation, mainly targeting agricultural soil sampling. Multiple zoning samplings are conducted, but all sampling is done at a depth of less than 3m in the soil surface layer. The sampling points are still relatively dense, suitable for small areas, but it does not take into account topographical variations and cannot guide costly borehole placement. Furthermore, the multiple zoning is unsuitable for borehole placement. CN111521754A discloses a preliminary sampling point layout method for soil pollution investigation at coking plant sites. Based on the coking plant's process flow, pollutant diffusion model, and sampling point scale regulations, a model for the number and accuracy of sampling points is established. The number of sampling points is determined by considering local spatial variability, controlling sampling costs. The method uses mathematical modeling, resulting in relatively accurate conclusions, which is worth referencing. However, due to insufficient sampling depth, it cannot be compared with borehole data, resulting in poor quantitative reference value. The article "Exploration of Soil Field Sampling Point Layout Methods in Eastern Henan Province Supported by GIS" uses a 2km*2km grid layout method based on GIS data to cover all land types in the modeled area, thus improving the local soil map. However, this method has high requirements for the matching of the modeled area itself and is not applicable to other sites, so it cannot be generalized. The article "Construction and Verification of an Optimized Method for Densified Sampling Point Layout in Soil Pollution Investigation" addresses the problem that the estimation accuracy of pollutant extent is insufficient for remediation. Based on preliminary investigation, it first predicts the probability of soil pollution and then conducts densified sampling point layout. This method has high accuracy and is a good method for soil sampling point layout, but it cannot provide a reference for high-cost projects such as borehole drilling.

[0007] Therefore, there is currently no suitable borehole placement method for hydrogeological modeling needs, especially a lack of an economical and effective method specifically for modeling. Boreholes differ significantly from general soil sampling in that they are costly, difficult to maintain, and prone to introducing new contamination. The number of boreholes must be small and precise, and cannot be simply increased or decreased based on basic background conditions such as topography, lest it affect the modeling results. Therefore, to fill this gap, this invention provides an effective borehole placement method suitable for hydrogeological modeling needs, solving the problem of the lack of a unified method for stratigraphic borehole placement during modeling. Furthermore, by considering the area and elevation differences of the modeling area, the placement method becomes more specific. Calculations show that the overall number of boreholes is not large, meeting the accuracy and economic requirements of modeling, and requiring minimal preliminary research, thus saving manpower and resources. Summary of the Invention

[0008] To address the aforementioned technical problems, this invention provides a borehole placement method suitable for hydrogeological modeling needs, resolving the current lack of guidance on borehole placement, which is costly and prone to secondary pollution. It provides an effective borehole placement method, particularly for situations requiring hydrogeological modeling of a site with high accuracy requirements for stratigraphic distribution and thickness variations within the model.

[0009] A borehole placement method suitable for hydrogeological modeling needs, the method comprising the following steps:

[0010] S1. Basic information about the survey and modeling site;

[0011] S2. Select a point layout scheme based on the area of ​​the modeling site;

[0012] S3. Generalize the modeling site into a rectangle and determine the length of the long side and the length of the short side of the generalized rectangle;

[0013] S4. Calculate the distance d between adjacent points based on the aspect ratio of the generalized rectangle;

[0014] S5. Determine the preliminary point layout method based on the area of ​​the modeling site and the distance d between adjacent points;

[0015] S6. Based on the existing borehole data and locations, as well as the slope variations in the modeling area, and in accordance with the principles of maximizing the use of known borehole points and increasing the density of borehole points on steep slopes, the preliminary borehole layout method is supplemented to form the final borehole layout method.

[0016] Furthermore, the point placement scheme includes a chessboard placement method and a serpentine placement method.

[0017] Furthermore, the basic information of the modeling site in step S1 includes the site's extent, elevation difference, publicly available borehole data and their locations within the site, and changes in site slope.

[0018] Furthermore, in step S2, the dividing line between the checkerboard and serpentine layout methods in the point-layout scheme is 1.5 km. 2 The modeled area.

[0019] Furthermore, the point layout scheme in step S2 is such that the modeling area is greater than 1.5 km². 2 Using a serpentine distribution method, with a distance of 1.5km or less. 2 The chessboard layout method is adopted.

[0020] Furthermore, in step S3, the method for generalizing the modeling site into a rectangle is as follows: connect the two points that are farthest apart in the modeling site, and define the length of the line connecting the two farthest points as the long side length of the generalized rectangle, with a length of 'a'. Draw the perpendicular bisector of the line connecting the two farthest points, and define the length between the two intersection points of the perpendicular bisector and the modeling site as the short side length, with a length of 'b'. Construct a rectangle using four points: the two farthest points in the modeling site, the intersection point of the perpendicular bisector of the line connecting the two farthest points and the modeling site.

[0021] Furthermore, in step S4, the distance d between adjacent points is obtained by calculating different cases based on the ratio of the long side length to the short side length of the generalized rectangle, with 4 as the critical value.

[0022] Furthermore, the specific calculation method for calculating based on the ratio of the longer side to the shorter side of the generalized rectangle is as follows:

[0023] When a / b≤4

[0024]

[0025] When a / b > 4

[0026]

[0027] In the formula: h is the elevation difference within the modeling area; C is the confidence interval.

[0028] Furthermore, the confidence interval C takes the value of 0.8-1.

[0029] Furthermore, in the final drilling point layout method in step S6, when the site slope changes uniformly, it is not necessary to perform additional densification of the determined preliminary point layout method.

[0030] Furthermore, in the drilling method, the drilling depth is the minimum depth to penetrate the waterproof layer.

[0031] Furthermore, in step S6, the determined preliminary point layout method is supplemented. The supplementation is not to adjust the original point layout, but to densify and supplement the point layout.

[0032] Beneficial effects: This paper provides an effective method for borehole point layout. First, a checkerboard or serpentine layout method is selected based on the size of the modeling area. Then, the modeling site is generalized into a simple rectangular area, and calculations are performed based on the aspect ratio of the rectangle. Next, the layout interval is calculated using mathematical formulas based on the elevation difference of the modeling site, the length of the shorter side of the rectangle, and confidence intervals. Finally, this is combined with existing borehole points and slope conditions to obtain the final layout scheme. This solves the problem of the lack of a unified layout method for original geological borehole data during modeling. Furthermore, by considering the area and elevation difference of the modeling area, the layout method becomes more targeted. Calculations show that the overall number of layout points is relatively small, meeting the accuracy and economic requirements of modeling. Attached Figure Description

[0033] Figure 1 A flowchart illustrating this method;

[0034] Figure 2 A diagram illustrating the chessboard layout method;

[0035] Figure 3 A diagram illustrating the serpentine dot pattern.

[0036] Figure 4 A simplified rectangular schematic diagram of the modeling site. Detailed Implementation

[0037] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are only for explaining the invention and are not intended to limit the invention; that is, the described embodiments are merely some embodiments of the invention, and not all embodiments.

[0038] Implementation Case 1:

[0039] Borehole distribution in a hydrogeological model of a small, uniformly sloped plot of land.

[0040] First, we investigated the basic information of the modeling site and learned that: the site's x and y coordinates are [not specified], and the area of ​​the plot is approximately 1.5 km². 2 The elevation difference between the highest and lowest points of the site is 50m; there is no publicly available data on boreholes within the site area; the slope of the site changes relatively evenly, with no obvious sudden bulges or depressions.

[0041] Because the site area is less than or equal to 1.5 km² 2 The checkerboard layout method is adopted; the modeling area is generalized as a rectangle, and the two points farthest apart within the modeling area are connected by a line, defined as the longer side with length a = 50m. The intersection of the perpendicular bisector of the longer side and the modeling area is connected by a line, defined as the shorter side with length b = 27m. Since a / b < 4, according to the formula...

[0042] Substituting a confidence level C of 1, the calculated point spacing is: d = 22.91m.

[0043] Based on the principles of maximizing the use of known borehole data and increasing the density of drilling points on steep slopes, the final drilling point layout is a checkerboard pattern with a spacing of 22.91m. Due to the uniform slope variation, no additional density drilling is required.

[0044] Implementation Case 2:

[0045] Borehole distribution in a hydrogeological model of a large area of ​​uniformly sloping land.

[0046] First, we investigated the basic information of the modeling site and learned that: the site's x and y coordinates are [not specified], and the area of ​​the plot is approximately 2.5 km². 2 The elevation difference between the highest and lowest points of the site is 50m. There are two publicly available boreholes, X1 and X2, within the site area. The slope of the site changes relatively evenly, without any obvious sudden bulges or depressions.

[0047] Because the site area is greater than 1.5km 2 The serpentine point layout method is then adopted; the modeling site is generalized into a rectangle, and the two points farthest apart within the modeling site are connected by a line, defined as the longer side with length a = 75m. The intersection of the perpendicular bisector of the longer side and the modeling site is connected by a line, defined as the shorter side with length b = 27m. Since a / b < 4, according to the formula...

[0048] Substituting a confidence level C of 1, the calculated point spacing is: d = 22.91m.

[0049] Based on the principles of maximizing the use of known borehole data and increasing the density of boreholes on steep slopes, the final borehole layout scheme is a serpentine method with a spacing of 22.91m. Existing boreholes will be used to supplement the layout, and no additional density of boreholes will be added due to the uniform slope variation.

[0050] Implementation Case 3:

[0051] Borehole distribution in a hydrogeological model of a long, narrow, slope-variable landmass.

[0052] First, we investigated the basic information of the modeling site and learned that: the site's x and y coordinates are [not specified], and the area of ​​the plot is approximately 1.5 km². 2 The elevation difference between the highest and lowest points of the site is 50m. There are two publicly available boreholes X1 and X2 within the site area. The site slope varies greatly, and there is a noticeable sudden bulge on the south side of the site.

[0053] Because less than or equal to 1.5km 2The chessboard layout method is adopted; the modeling area is generalized as a rectangle, and the two points farthest apart within the modeling area are connected by a line, defined as the longer side with length a = 60m. The intersection of the perpendicular bisector of the longer side and the modeling area is connected by a line, defined as the shorter side with length b = 14m. Since a / b > 4, according to the formula...

[0054] Substituting a confidence level C of 0.8, the calculated point spacing is: d = 14.25m.

[0055] Based on the principles of maximizing the use of known borehole data and increasing the density of borehole locations on steep slopes, the final layout scheme is a checkerboard method with a spacing of 17.82m. Existing boreholes will be supplemented, and due to the large changes in slope, additional denser boreholes will be placed on the south side of the site.

[0056] Implementation Case 4:

[0057] Borehole distribution in a hydrogeological model of a large, elongated, slope-variable landmass.

[0058] First, we investigated the basic information of the modeling site and learned that: the site's x and y coordinates are [not specified], and the area of ​​the plot is approximately 2.5 km². 2 The elevation difference between the highest and lowest points of the site is 50m. There are two publicly available boreholes X1 and X2 within the site area. The site slope varies greatly, and there is a noticeable sudden bulge on the south side of the site.

[0059] Because it is greater than 1.5km 2 The serpentine point layout method is then adopted; the modeling site is generalized into a rectangle, and the two points farthest apart within the modeling site are connected by a line, defined as the long side with length a = 60m. The intersection of the perpendicular bisector of the long side and the modeling site is connected by a line, defined as the short side with length b = 14m. Since a / b > 4, according to the formula...

[0060] Substituting a confidence level C of 0.8, the calculated point spacing is: d = 14.25m.

[0061] Based on the principles of maximizing the use of known borehole data and increasing the density of borehole locations on steep slopes, the final borehole location scheme is a serpentine method with a spacing of 14.25m. Existing boreholes will be used to supplement the existing ones, and due to the large changes in slope, additional borehole locations will be added on the south side of the site.

[0062] Implementation Case 5:

[0063] Borehole distribution in a hydrogeological model of a large, elongated, and high-altitude landmass.

[0064] First, we investigated the basic information of the modeling site and learned that: the site's x and y coordinates are [not specified], and the area of ​​the plot is approximately 2.5 km². 2The elevation difference between the highest and lowest points of the site is 150m. There are two publicly available boreholes, X1 and X2, within the site area. The site slope varies greatly, and there is a noticeable sudden bulge on the south side of the site.

[0065] Because it is greater than 1.5km 2 The serpentine point layout method is then adopted; the modeling site is generalized into a rectangle, and the two points farthest apart within the modeling site are connected by a line, defined as the long side with length a = 60m. The intersection of the perpendicular bisector of the long side and the modeling site is connected by a line, defined as the short side with length b = 14m. Since a / b > 4, according to the formula...

[0066] Substituting a confidence level C of 1, the calculated point spacing is: d = 10.5m.

[0067] Based on the principles of maximizing the use of known borehole data and increasing the density of borehole locations on steep slopes, the final borehole location scheme is a serpentine method with a spacing of 10.5m. Existing boreholes will be used to supplement the existing ones, and additional boreholes will be added on the south side of the site due to the large changes in slope.

[0068] Of course, the above description is not intended to limit the present invention, and the present invention is not limited to the examples given above. Any changes, modifications, additions or substitutions made by those skilled in the art within the scope of the present invention should also fall within the protection scope of the present invention.

Claims

1. A borehole layout method suitable for hydrogeological modeling needs, characterized in that, The point placement method includes the following steps: S1. Basic information about the survey and modeling site; S2. Select a point layout scheme based on the area of ​​the modeling site; S3. Generalize the modeling site into a rectangle and determine the length of the long side and the length of the short side of the generalized rectangle; S4. Calculate the distance d between adjacent points based on the aspect ratio of the generalized rectangle; S5. Determine the preliminary point layout method based on the area of ​​the modeling site and the distance d between adjacent points; S6. Based on the existing borehole data and locations, as well as the slope variations in the modeling area, and in accordance with the principles of maximizing the use of known borehole points and increasing the density of borehole points on steep slopes, the preliminary borehole layout method is supplemented to form the final borehole layout method.

2. The borehole layout method suitable for hydrogeological modeling requirements according to claim 1, characterized in that: The point placement schemes include the chessboard placement method and the serpentine placement method.

3. The borehole layout method suitable for hydrogeological modeling requirements according to claim 1, characterized in that: The basic information of the modeling site in step S1 includes the site's extent, elevation difference, publicly available borehole data and their locations within the site, and changes in site slope.

4. The borehole layout method suitable for hydrogeological modeling requirements according to claim 2, characterized in that: In step S2, the boundary between the checkerboard and serpentine layout methods is 1.5 km. 2 The modeled area.

5. A borehole layout method suitable for hydrogeological modeling requirements according to claim 4, characterized in that: The point layout scheme in step S2 is as follows: the modeling area is greater than 1.5km². 2 Using a serpentine distribution method, with a distance of 1.5km or less. 2 The chessboard layout method is adopted.

6. The borehole layout method suitable for hydrogeological modeling requirements according to claim 1, characterized in that: In step S3, the method for generalizing the modeling site into a rectangle is as follows: connect the two points that are farthest apart in the modeling site. The length of the line connecting the two farthest points is defined as the long side length of the generalized rectangle, with a length of 'a'. Draw the perpendicular bisector of the line connecting the two farthest points. The length between the two intersection points of the perpendicular bisector and the modeling site is defined as the short side length, with a length of 'b'. Construct a rectangle using the four points: the two farthest points in the modeling site, the intersection point of the perpendicular bisector of the line connecting the two farthest points and the modeling site.

7. A borehole layout method suitable for hydrogeological modeling requirements according to claim 1, characterized in that: In step S4, the distance d between adjacent points is obtained by calculating different cases based on the ratio of the long side to the short side of the generalized rectangle, with 4 as the critical value.

8. A borehole layout method suitable for hydrogeological modeling requirements according to claim 7, characterized in that: The specific calculation method based on the ratio of the long side to the short side of the generalized rectangle is as follows: When a / b≤4 When a / b > 4 In the formula: h is the elevation difference within the modeling area; C is the confidence interval.

9. A borehole layout method suitable for hydrogeological modeling requirements according to claim 8, characterized in that: The confidence interval C ranges from 0.8 to 1.

10. A borehole layout method suitable for hydrogeological modeling requirements according to claim 1, characterized in that: In step S6, when the site slope changes uniformly, it is not necessary to further densify the drilling points in the final drilling method.

11. A borehole layout method suitable for hydrogeological modeling requirements according to claim 1, characterized in that: In the final drilling method, the drilling depth is the minimum depth to penetrate the waterproof layer.

12. A borehole layout method suitable for hydrogeological modeling requirements according to any one of claims 1-11, characterized in that: In step S6, the determined preliminary point layout method is supplemented. The supplementation is not to adjust the original point layout, but to densify the point layout and supplement the point layout.

Images