A method for predicting small structures based on fractal theory

Abstract

This invention discloses a method for predicting small-scale geological structures based on fractal theory, comprising: detecting the distribution of faults in the study area; calculating the fault information dimension based on fractal theory and drawing a fault information dimension cloud map; drilling exploratory boreholes in the study area and performing in-hole ultrasonic imaging; calculating the joint information dimension within the boreholes based on fractal theory and calculating the joint surface density within the boreholes; establishing a functional relationship between the fault information dimension and the joint information dimension within the boreholes, using the joint surface density within the boreholes as a bridge; calculating the subsurface joint information dimension of the radiation area based on the fault information dimension and drawing a reservoir area joint information dimension cloud map; and analyzing the reservoir area joint information dimension cloud map to predict small-scale geological structures. This invention can predict small-scale geological structures that cannot be detected by traditional exploration techniques, identify seawater intrusion channels, reduce the risk of seawater intrusion, and is applicable to coastal underground engineering projects with seawater intrusion risks.

Description

Technical Field

[0001] This invention relates to the field of small-scale geological structure prediction technology, and in particular to a method for predicting small-scale structures based on fractal theory. Background Technology

[0002] Coastal underground engineering projects are susceptible to seawater intrusion. Seawater contains high levels of harmful ions such as chloride and bromide, which can easily contaminate stored resources like petroleum and corrode the structures within these projects. Therefore, seawater intrusion should be minimized. Small-scale structures can easily create water-conducting channels and high-permeability zones, increasing the risk of seawater intrusion. It is necessary to identify the distribution of small-scale structures and implement targeted measures to prevent seawater intrusion. This places higher demands on the accuracy of small-scale structure detection.

[0003] Currently, shallow seismic wave reflection, high-density electrical resistivity tomography, and borehole drilling are commonly used exploration methods to detect small geological structures. However, these methods are limited by insufficient detection accuracy and the inherent concealment of small structures, necessitating supplementary analysis. Previous research has shown that the distribution and development of faults and joints exhibit self-similarity, conforming to the requirements of fractal theory. Based on existing geophysical drilling results, fractal theory can be used to predict small geological structures that traditional exploration techniques cannot detect, thereby identifying seawater intrusion channels and reducing the risk of seawater intrusion. Summary of the Invention

[0004] This invention provides a method for predicting small-scale geological structures based on fractal theory, enabling the prediction of small-scale geological structures that cannot be detected by traditional exploration techniques, identifying seawater intrusion channels, and reducing the risk of seawater intrusion.

[0005] To achieve the above objectives, the present invention provides the following technical solution:

[0006] A method for predicting small-scale structures based on fractal theory, comprising:

[0007] The distribution of faults in the study area was detected using pre-set geophysical methods; the faults in the study area were divided into cells, and the fault information dimension was calculated based on fractal theory to draw a fault information dimension cloud map;

[0008] Exploration boreholes were drilled in the study area to conduct in-hole ultrasonic imaging; the in-hole ultrasonic imaging results were divided into cells, and the joint information dimension in the borehole was calculated based on fractal theory, and the joint surface density in the borehole was also calculated.

[0009] Using the joint surface density within the borehole as a bridge, a functional relationship between the fault information dimension and the joint information dimension within the borehole is established; the underground joint information dimension of the radiation area is calculated by combining the fault information dimension, and a cloud map of the joint information dimension of the reservoir area is drawn.

[0010] By analyzing the cloud map of joint information in the reservoir area, prediction of small-scale structures can be achieved.

[0011] Furthermore, the preset geophysical exploration methods include shallow seismic wave reflection, shallow seismic wave refraction, and high-density electrical resistivity tomography; the use of preset geophysical exploration methods to detect fault distribution in the study area includes:

[0012] By combining the results of shallow seismic wave reflection, shallow seismic wave refraction, and high-density electrical resistivity tomography, geophysical anomaly zones are analyzed and plotted on engineering geological maps.

[0013] Based on the geophysical anomaly areas and the results of on-site geological exploration, a fault distribution map was drawn.

[0014] Furthermore, the step of dividing the fault in the study area into cells, calculating the fault information dimension based on fractal theory, and drawing a fault information dimension cloud map includes:

[0015] Based on the design scope of the reservoir area and the distribution area of ​​faults, and with the principle of including as much fault area information as possible while minimizing the inclusion of blank spaces outside the area, the reservoir area is divided into several cells;

[0016] The divided cells are subdivided more than three times using the bisection method, and the grid scale ε is taken as the corresponding subdivision multiple. The fault information dimension is calculated based on fractal theory.

[0017] Based on the calculated fault information dimensions, draw a fault information dimension cloud map of the reservoir area.

[0018] Furthermore, the dimension of the fault information is calculated using the following formula:

[0019]

[0020] Among them, D f Let I be the fractal dimension of the fault information, ε be the grid scale, and I be the value of the fractal dimension. f (ε) represents the total fault information quantity when the grid size of a single cell is ε; the total fault information quantity I f The formula for calculating (ε) is:

[0021]

[0022] Among them, P i (ε) represents the total fault length contained in the i-th cell when the grid scale is ε.

[0023] Furthermore, the step of dividing the borehole ultrasonic imaging results into cell units and calculating the joint information dimension within the borehole based on fractal theory includes:

[0024] Based on the intra-hole ultrasonic imaging baseline, draw the joint polyline;

[0025] With the borehole diameter d as the width, and not exceeding the results of in-hole ultrasonic imaging. Figure 1 / 3 Length a is the length, and the intra-orifice ultrasonic imaging result image is divided into several cells;

[0026] The divided cells are subdivided more than three times using the bisection method, and the grid scale ε is taken as the corresponding subdivision multiple. The joint information dimension inside the borehole is calculated based on fractal theory.

[0027] Furthermore, the joint information dimension within the borehole is calculated using the following formula:

[0028]

[0029] Among them, D j Let ε be the fractal dimension of the joint information within the borehole, and I be the grid scale. j (ε) represents the total information content of joints within the borehole when the grid size of a single cell is ε; the total information content of joints within the borehole I j The formula for calculating (ε) is:

[0030]

[0031] Among them, Q i (ε) represents the total joint length contained in the i-th grid when the grid scale is ε.

[0032] Furthermore, the joint surface density k within the borehole is calculated using the following formula:

[0033]

[0034] Where l is the total length of the joints within a single cell, and s is the area of ​​a single cell.

[0035] Furthermore, the establishment of a functional relationship between the fault information dimension and the borehole joint information dimension, using the borehole joint surface density as a bridge, includes:

[0036] The joint information dimension and joint surface density of all boreholes were statistically analyzed, and a functional relationship between the joint information dimension and the joint surface density of boreholes was constructed.

[0037] Establish a functional relationship between fault information dimension and joint surface density within the borehole;

[0038] Based on the established functional relationship between the joint information dimension and the joint surface density within the borehole, as well as the functional relationship between the fault information dimension and the joint surface density within the borehole, the functional relationship between the fault information dimension and the joint information dimension within the borehole is established using the joint surface density within the borehole as a bridge.

[0039] Furthermore, analysis of the joint information cloud map in the reservoir area enables the prediction of small-scale structures, including:

[0040] In the analysis of the joint information cloud map of the reservoir area, the region with a joint information dimension higher than that of the surrounding area of ​​the known fault zone is designated as a small-scale structural prediction zone.

[0041] Furthermore, after achieving the prediction of small-scale structures, the method further includes:

[0042] Exploratory boreholes were drilled in the study area to verify the accuracy of the small-scale structural prediction results.

[0043] The beneficial effects of the technical solution provided by this invention include at least the following:

[0044] This invention utilizes fractal theory to calculate the dimensions of known fault information and borehole joint information, respectively. It then establishes a functional relationship between these two dimensions using the borehole joint surface density as a bridge, and generates a cloud map of the joint information dimensions in the reservoir area. Ultimately, this enables the prediction of small-scale geological structures, identifies seawater intrusion channels, and reduces the risk of seawater intrusion. This method is particularly suitable for coastal underground engineering projects at risk of seawater intrusion. Attached Figure Description

[0045] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0046] Figure 1 This is a schematic diagram of the execution flow of the small-scale structure prediction method based on fractal theory provided in an embodiment of the present invention;

[0047] Figure 2 This is a fault grid diagram provided in an embodiment of the present invention;

[0048] Figure 3 This is a fractal diagram provided in an embodiment of the present invention;

[0049] Figure 4 This is a schematic diagram of the intra-hole ultrasonic imaging grid provided in an embodiment of the present invention;

[0050] Figure 5 This is a predicted cloud map after processing of joint information dimension data provided in the embodiments of the present invention. Detailed Implementation

[0051] To make the objectives, technical solutions, and advantages of the present invention clearer, the embodiments of the present invention will be described in further detail below with reference to the accompanying drawings.

[0052] This embodiment provides a small-scale structural prediction method based on fractal theory for coastal underground engineering projects. This method analyzes and maps the joint information in the reservoir area to predict small-scale structures, identify seawater intrusion channels, and reduce the risk of seawater intrusion. It is particularly suitable for coastal underground engineering projects at risk of seawater intrusion. Specifically, the execution flow of this method is as follows: Figure 1 As shown, it includes the following steps:

[0053] S1, using pre-set geophysical methods to detect the distribution of faults in the study area;

[0054] In this embodiment, the geophysical methods employed include shallow seismic wave reflection, shallow seismic wave refraction, and high-density electrical resistivity tomography (EDT). The process of detecting the fault distribution in the study area using the preset geophysical methods includes:

[0055] Step 1: Combine the results of shallow seismic wave reflection, shallow seismic wave refraction, and high-density electrical resistivity tomography to analyze the geophysical anomaly areas and plot them on the engineering geological map.

[0056] Step 2: Combine the results of geophysical anomaly zones and on-site geological exploration to draw a fault distribution map.

[0057] S2, divide the faults in the study area into cells, calculate the fault information dimension based on fractal theory, and draw a fault information dimension cloud map;

[0058] Specifically, in this embodiment, the implementation of S2 includes the following steps:

[0059] Step 1: Based on the design scope of the reservoir area and the distribution area of ​​faults, and with the principle of including as much fault area information as possible while minimizing the inclusion of blank spaces outside the area, divide the reservoir area into several cells with a side length of 'a'.

[0060] Step 2: Subdivide the divided cells at least three times using a bisection method, with the grid scale ε corresponding to the subdivision factor, and calculate the fault information dimension D based on fractal theory. f ;

[0061] Specifically, in this embodiment, the tomographic cell division of the study area is as follows: Figure 2 As shown, the library area is divided into 176 cells with a side length of 125m; the fractal diagram of the cell division is as follows. Figure 3 As shown, the cell is subdivided three times using the bisection method, with the grid scale ε taking the basic values ​​of the bisection method as 1 / 2, 1 / 4, 1 / 8, and 1 / 16, respectively.

[0062] The fault information dimension is calculated using the following formula:

[0063]

[0064] Among them, D f Let I be the fractal dimension, ε be the grid scale, and I be the fractal dimension. f (ε) represents the total fault information when the grid size of one cell is ε; Total fault information I f The formula for calculating (ε) is:

[0065]

[0066] Among them, P i (ε) represents the total fault length contained in the i-th cell when the grid scale is ε.

[0067] Step 3, based on the calculated fault information dimension D f Draw a three-dimensional cloud map of fault information in the reservoir area.

[0068] S3, drilling exploration boreholes in the study area to conduct in-hole ultrasonic imaging;

[0069] S4. Using the borehole ultrasonic imaging results as the base map, cell division is performed, and the dimension of joint information in the borehole is calculated based on fractal theory.

[0070] Specifically, in this embodiment, the implementation of S4 includes the following steps:

[0071] Step 1: Draw the joint polyline based on the intra-hole ultrasonic imaging base map;

[0072] Step 2, using the borehole diameter d as the width, and not exceeding the results of the borehole ultrasonic imaging. Figure 1 / 3 The length a is the length, and the ultrasonic imaging result image inside the hole is divided into several cells; in this embodiment, d is 75mm and a is 10m.

[0073] Step 3: Subdivide the divided cells at least three times using a bisection method, with the grid scale ε taking the corresponding subdivision factor, and calculate the dimension D of the borehole joint information based on fractal theory. j In this embodiment, the grid scale ε is taken as the basic values ​​of the bisection method: 1 / 2, 1 / 4, 1 / 8, and 1 / 16, respectively.

[0074] Specifically, the intra-aperture ultrasonic imaging grid is illustrated as follows: Figure 4 As shown.

[0075] The joint information dimension within the borehole is calculated using the following formula:

[0076]

[0077] Among them, D j Let I be the fractal dimension, ε be the grid scale, and I be the fractal dimension. j(ε) represents the total information content of joints within the borehole when the grid size of a single cell is ε; the total information content of joints within the borehole is I. j The formula for calculating (ε) is:

[0078]

[0079] Among them, Q i (ε) represents the total joint length contained in the i-th grid when the grid scale is ε.

[0080] S5, calculate the density of joint surfaces within the borehole using the following formula:

[0081]

[0082] Where k is the joint surface density within the borehole (m³ / s²). -1 ), where l is the total length of the joints within a single cell (m), and s is the area of ​​a single cell (m²). -2 ).

[0083] S6, Statistically calculate the joint information dimension and joint surface density of all boreholes, and construct the functional relationship between the joint information dimension and the joint surface density of boreholes;

[0084] S7, Establish the functional relationship between fault information dimension and joint surface density in borehole;

[0085] S8. Using the joint surface density within the borehole as a bridge, a functional relationship between the fault information dimension and the joint information dimension within the borehole is established.

[0086] S9, combine fault information dimension to calculate underground joint information dimension of the radiation area, and draw joint information dimension cloud map of reservoir area;

[0087] Among them, the joint information cloud map is as follows: Figure 5 As shown.

[0088] S10 analyzes the cloud map of joint information in the reservoir area to predict small-scale structures.

[0089] Specifically, in this embodiment, S10 is as follows:

[0090] The key analysis focuses on the joint information cloud map of the reservoir area. The region where the joint information dimension of the borehole-affected area is higher than that of the joint information dimension around the known fault area is designated as a small-scale structural prediction area.

[0091] Furthermore, after achieving the prediction of small-scale structures, the method may further include:

[0092] S11, exploratory boreholes were drilled in the study area to verify the accuracy of the small-scale structural prediction results.

[0093] After predicting small structures using the above method, on-site construction verification revealed that most of the predicted high-risk areas did indeed have small structures, indicating a good prediction effect.

[0094] In summary, this embodiment uses fractal theory to calculate the dimensions of known fault information and borehole joint information, respectively. It then establishes a functional relationship between these two dimensions using the borehole joint surface density as a bridge, and plots a cloud map of the reservoir area's joint information dimensions. Ultimately, this method enables the prediction of small-scale geological structures, identifies seawater intrusion channels, and reduces the risk of seawater intrusion. This method is particularly suitable for coastal underground engineering projects at risk of seawater intrusion.

[0095] Furthermore, it should be noted that, in this document, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or terminal device that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or terminal device. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or terminal device that includes said element.

[0096] Finally, it should be noted that the above description represents a preferred embodiment of the present invention. It should be pointed out that although preferred embodiments have been described, those skilled in the art, once they understand the basic inventive concept of the present invention, can make various improvements and modifications without departing from the principles described herein. These improvements and modifications should also be considered within the scope of protection of the present invention. Therefore, the appended claims are intended to be interpreted as including both the preferred embodiments and all changes and modifications falling within the scope of the embodiments of the present invention.

Claims

1. A small-scale structure prediction method based on fractal theory, characterized by, The method comprises the following steps: detecting the fault distribution in the research area by using a preset geophysical prospecting means; dividing the faults in the research area into unit cells, and calculating the fault information dimension based on the fractal theory, and drawing a fault information dimension cloud chart, which comprises the following steps: dividing the reservoir area into a plurality of unit cells according to the criterion of as completely containing the fault area information as possible and as few as possible containing the space outside the area; subdividing the divided unit cells by dichotomy for more than three times, and taking the grid scale ε as the corresponding subdivision multiple, and calculating the fault information dimension based on the fractal theory; and drawing a fault information dimension cloud chart of the reservoir area according to the calculated fault information dimension; In the research area construction exploration drilling, carry out hole ultrasonic imaging; on the hole ultrasonic imaging results map unit cell division, based on the fractal theory calculation drilling joint information dimension, and calculate the joint surface density in the drill hole, including: according to the hole ultrasonic imaging base map, draw joint polyline; with the drill diameter d as the width, with the length a not more than 1 / 3 of the hole ultrasonic imaging result map as the length, the hole ultrasonic imaging result map is divided into several unit cells; the unit cell is divided by the bisection method for more than 3 times, the grid scale ε is respectively taken as the corresponding subdivision multiple, based on the fractal theory to calculate the joint information dimension in the drill hole; the joint surface density k in the drill hole is calculated by the following formula: Wherein, l is the total length of the joint in a unit cell, s is the area of a unit cell; establishing a functional relationship between the fault information dimension and the joint information dimension in the borehole by taking the joint surface density in the borehole as a bridge; calculating the joint information dimension in the radiation area based on the fault information dimension, and drawing a joint information dimension cloud chart of the reservoir area; analyzing the joint information dimension cloud chart of the reservoir area to realize the prediction of small structures; the functional relationship between the fault information dimension and the joint information dimension in the borehole is established by taking the joint surface density in the borehole as a bridge, which comprises the following steps: statistically analyzing the joint information dimension and the joint surface density in the borehole, and constructing a functional relationship between the joint information dimension in the borehole and the joint surface density in the borehole; establishing a functional relationship between the fault information dimension and the joint surface density in the borehole; and based on the established functional relationship between the joint information dimension in the borehole and the joint surface density in the borehole, and the functional relationship between the fault information dimension and the joint surface density in the borehole, the functional relationship between the fault information dimension and the joint information dimension in the borehole is established by taking the joint surface density in the borehole as a bridge; the analysis of the joint information dimension cloud chart of the reservoir area to realize the prediction of small structures comprises the following steps: analyzing the area where the joint information dimension in the borehole is higher than the joint information dimension around the proven fault area in the joint information dimension cloud chart of the reservoir area, and defining the area as a small structure prediction area.

2. The method of claim 1, wherein the fractal theory-based small structure prediction method is characterized by, the preset geophysical prospecting means comprises shallow seismic wave reflection, shallow seismic wave refraction and high-density electrical method; the detection of the fault distribution in the research area by using the preset geophysical prospecting means comprises the following steps: analyzing the geophysical prospecting anomaly area based on the geophysical prospecting results of shallow seismic wave reflection, shallow seismic wave refraction and high-density electrical method, and drawing the geophysical prospecting anomaly area on the engineering geological map; combining the geophysical prospecting anomaly area and the on-site geological exploration results, and drawing a fault distribution map.

3. The method of claim 1, wherein the fractal theory-based small structure prediction method is characterized by, the fault information dimension is calculated by the following formula: Among them, D f Let I be the fractal dimension of the fault information, ε be the grid scale, and I be the value of the fractal dimension. f (ε) represents the total fault information quantity when the grid size of a single cell is ε; the total fault information quantity I f The formula for calculating (ε) is: where P i (ε) is the total length of faults contained in the i-th grid cell at grid scale ε.

4. The method of claim 1, wherein the fractal theory-based small structure prediction method is characterized by, the joint information dimension in the borehole is calculated by the following formula: Wherein, D j is the fracturing information dimension value in the borehole, ε is the grid scale, I j (ε) is the total information amount of the fractures in the borehole when the grid scale of one unit cell is ε; the total information amount I j (ε) of the fractures in the borehole is calculated by the following formula: where Q i (e) is the total length of joints contained in the i-th grid at the grid scale of ε.

5. The small-scale structure prediction method based on fractal theory according to any one of claims 1 to 4, characterized by, after realizing the prediction of small structures, the method further comprises the following steps: constructing an exploration borehole in the research area to verify the accuracy of the prediction results of small structures.

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