Coal seam roof and floor equivalent lithology determination method based on borehole column chart information

Abstract

The present application relates to the technical field of coal mine geology engineering, in particular to a coal seam roof and floor equivalent lithology determination method based on drilling columnar chart information, which can extract all straight line objects and text object data in the drilling columnar chart in a software manner, match the text and rock stratum information by classifying the text objects into the areas divided by the corresponding vertical straight lines according to the horizontal positions, construct a table framework combined with the straight line objects, extract the sequence number, dip angle, true thickness and lithology data of each rock stratum, determine the coal seam roof and floor equivalent lithology based on the lithology description recognition, lithology classification rules and algorithms, and finally output the structured rock stratum data and equivalent lithology results. The present application has the beneficial effects of greatly improving the efficiency of the exploration drilling columnar chart information reading and processing, significantly reducing the subjective error of manual interpretation, realizing the accurate analysis of the rock stratum data, ensuring the accuracy and consistency of the coal seam roof and floor equivalent lithology determination, and laying an important foundation for the mine gas accuracy prediction.

Description

Technical Field

[0001] This invention relates to the field of coal mine geological engineering technology, specifically a method for determining the equivalent lithology of the top and bottom plates of coal seams based on borehole columnar section information. Background Technology

[0002] In the coal mining process, gas outbursts at the mining and tunneling faces are significantly affected by the lithological combination characteristics of the coal seam's roof and floor. Equivalent lithology is an analytical method specifically designed to reflect the lithological combination characteristics of the coal seam's roof and floor. This method equates various lithologies of the coal seam and its mining activities within the image range to a single lithology.

[0003] Lithological equivalence is determined based on the columnar section of exploration boreholes in coal-bearing strata. Typically, a coal mine requires hundreds of exploration boreholes, and tens of thousands of borehole columnar section data need to be processed. Currently, this is done manually, based on experience, which is time-consuming and labor-intensive, and the results vary from person to person. A unified automatic identification model has not yet been established, which makes it difficult to meet the needs of accurate and intelligent development of mine gas prediction, and directly affects the reliability of mine gas prevention and control planning and measures. Summary of the Invention

[0004] To address the shortcomings of existing technologies, the purpose of this invention is to provide a method for determining the equivalent lithology of the roof and floor of coal seams based on borehole columnar section information, achieving efficient extraction of strata information and rule-based classification of equivalent lithology. This method can automatically parse borehole columnar section data, extracting strata numbers, lithology names, stratigraphic positions, thicknesses, and dip angles. Combined with preset equivalent lithology determination rules, it determines the equivalent lithology of each coal seam's roof and floor, constructing a structured data table. Driven by a rule engine, it achieves batch processing of multi-bore data and output of equivalent lithology results, forming a unified database. By integrating borehole columnar section image recognition and strata parameter quantification, it achieves automated extraction of strata information and determination of equivalent lithology, significantly improving data processing efficiency and result consistency, and providing reliable geological basis for gas prediction at different mining stages.

[0005] The technical solution adopted by this invention to solve its technical problem is:

[0006] A method for determining the equivalent lithology of the roof and floor of a coal seam based on borehole columnar section information includes:

[0007] S1. Extract information of all straight line objects from the DXF file of the borehole column chart, identify vertical and horizontal line segments based on the geometric features of the straight line objects, and construct the table framework of the borehole column chart based on the vertical and horizontal line segments.

[0008] S2. Extract information of all text objects from the DXF file of the borehole column chart;

[0009] S3. Determine the horizontal coordinates of the insertion points for the four header texts in the text object: layer number, dip angle, true thickness, and lithology name.

[0010] S4. Based on the determined horizontal coordinates of the insertion point, the header text is placed into the corresponding column area in the table frame to complete the data matching of layer number, dip angle, true thickness and lithology name;

[0011] S5. Traverse the data corresponding to each row of cells, extract the layer number, dip angle, true thickness and lithology name data, and construct a list of rock strata information;

[0012] S6. Identify coal-bearing sections based on lithology names in the strata information list, and determine the location of the target coal seam and its adjacent upper and lower strata.

[0013] S7. Analyze the lithological characteristics of the roof and floor within the set range of the target coal seam according to the set geological rules, and determine the equivalent lithology of the roof and floor.

[0014] S8 outputs a structured rock strata data table and the equivalent lithology determination results for the roof and floor of each coal seam.

[0015] As a preferred embodiment, a further technical solution of the present invention is:

[0016] Preferably, S1 specifically includes:

[0017] Parse the straight line entities in the DXF file of the borehole column diagram to obtain the start and end coordinates of each line;

[0018] Calculate the slope of each straight line and, in conjunction with a set threshold, distinguish between vertical and horizontal line segments;

[0019] Determine the boundaries of each column in the table based on the horizontal coordinates of the vertical line segments, and establish a column range index for the table.

[0020] Based on the vertical coordinates of the horizontal line segments, determine the boundaries of each row in the table, and construct the table framework by combining the column range index and the boundaries of each row.

[0021] Preferably, S2 specifically includes:

[0022] Parse the text entities in the DXF file of the borehole column chart to obtain the text content and the coordinates of the text insertion point;

[0023] By combining font, layer, and location information, invalid annotations are filtered out, thus preserving text related to rock strata parameters;

[0024] Key fields such as layer number, dip angle, true thickness, and lithology name are extracted using character encoding recognition and Chinese word segmentation technology.

[0025] Preferably, S3 specifically includes:

[0026] The text elements with header features in the location file are matched with keywords such as layer number, dip angle, true thickness, and lithology name based on the text content of the text elements;

[0027] Obtain the horizontal coordinates of the insertion points for the four header texts: layer number, dip angle, true thickness, and lithology name, and establish the correspondence between the header texts and the horizontal coordinates of the insertion points.

[0028] By combining column range indexes to correct column header coordinate deviations, we can ensure accurate division of column regions for each field.

[0029] Preferably, S4 specifically includes:

[0030] The horizontal coordinates of the insertion point of each text object are compared with the column range index to determine the column range to which the text object belongs;

[0031] Based on the vertical coordinate range of the row boundary, the corresponding cell is matched to achieve spatial association between text content and table structure;

[0032] Correct misaligned or missing items according to the increasing pattern of the layer number to ensure that the data rows are completely aligned;

[0033] The final result is a structured stratum parameter table indexed by stratum number and containing fields for dip angle, true thickness, and lithology name.

[0034] Preferably, S5 specifically includes:

[0035] Read the matched structured data line by line, and extract the dip angle, true thickness and lithology name of each line in order of layer number;

[0036] Standardize the text content of each field, and unify the units and expression format;

[0037] For missing or outlier values, interpolation from adjacent layers or estimation based on geological patterns can be used to complete them;

[0038] The information is finally compiled into a complete list of rock strata, which serves as the basis for identifying the roof and floor of coal seams and classifying equivalent lithology.

[0039] Preferably, S6 specifically includes:

[0040] By using language processing techniques to analyze the lithological name field, coal-bearing fields and variant expressions are identified, thereby determining the coal-bearing intervals;

[0041] The coal seam intervals are divided according to the continuous distribution of the layer numbers, the location of the target coal seam is located, the lithological names and true thickness information of the adjacent rock layers above and below the target coal seam are extracted, and a sequence of adjacent rock layers with the target coal seam as the core is constructed.

[0042] Misjudgments are corrected based on the chronological order of sedimentary rock formation to ensure the accurate relationship between the upper and lower strata of the target coal seam.

[0043] Preferably, S7 specifically includes:

[0044] 1) Determine lithological classification

[0045] Based on the gas storage capacity and permeability of lithology, the lithologies with different names in the borehole column are divided into 6 categories: coarse sandstone, medium sandstone, medium-fine sandstone, fine sandstone, claystone, and thick mudstone.

[0046] 2) Determine the range of the equivalent rock strata.

[0047] Taking into account two factors: first, the range of the conventional roof and floor affected by mining activities as determined by the theory of mineral pressure; and second, whether there is contact with thick layers of medium-coarse sandstone in a specific area outside the conventional roof and floor range, as detailed below:

[0048] Tunneling condition: Equivalent thickness L of bottom plate f =3+2k f Equivalent thickness L of top plate r =5+3k r ;

[0049] Longwall mining conditions: Equivalent thickness F of the bottom plate f =5+2k f Equivalent thickness F of top plate r =10H≤40+5k r ;

[0050] Where H is the target coal seam thickness; k f It is the equivalent peripheral influence coefficient of the base plate. It mainly considers whether there is contact with thick medium-coarse sandstone within 2m outside the conventional top and bottom plate range. If there is contact with coarse sandstone and the thickness of coarse sandstone is not less than 5m, the value is 1. If there is contact with medium sandstone and the thickness of medium sandstone is not less than 8m, the value is 1. Otherwise, the value is 0.

[0051] k r It is the equivalent peripheral influence coefficient of the top plate. It mainly considers whether there is contact with thick medium-coarse sandstone within 5m outside the conventional top and bottom plate range. If there is contact with coarse sandstone and the thickness of coarse sandstone is not less than 5m, the value is 1. If there is contact with medium sandstone and the thickness of medium sandstone is not less than 8m, the value is 1. Otherwise, the value is 0.

[0052] 3) Determine the ranking priority for equivalent lithology naming.

[0053] Based on the degree of influence of various lithologies on gas outbursts in the mining space, the priority order is as follows: coarse sandstone > thick mudstone > medium sandstone > claystone > medium-fine sandstone > fine sandstone;

[0054] Special cases: When the mudstone layer is the immediate roof and its thickness is 0.6-2m, it is named claystone, with priority after medium sandstone and before medium-fine sandstone; if the thickness is ≥2m, it is named thick mudstone, with priority after coarse sandstone and before medium sandstone; if the mudstone layer is not the immediate roof of the coal seam, it is not considered. If it is below the coal seam floor, it is ranked after fine sandstone.

[0055] 4) Set equivalent lithological conditions

[0056] The equivalent ranges for coal seam recovery and tunneling roof and floor are determined separately:

[0057] Equivalent conditions for coarse sandstone: Hc = ∑hc + 0.5∑hz ≥ 3m;

[0058] Equivalent conditions for thick mudstone: the mudstone layer is the immediate top, and Hh≥2m;

[0059] Equivalent conditions for medium sandstone: Hz = ∑hz + 1.6∑hc ≥ 3m, and there is no equivalent thick mudstone.

[0060] Equivalent conditions for claystone: The mudstone layer is the immediate top, and 0.6m ≤ Hn < 2m;

[0061] Equivalent conditions for medium-fine sandstone: Hzx = ∑hzx + 1.4∑hz ≥ 3m, and no equivalent claystone exists;

[0062] Equivalent conditions for fine sandstone: None of the above equivalent lithologies exist;

[0063] Where Hc represents the equivalent thickness of coarse sandstone; ∑hc represents the cumulative thickness of the coarse sandstone layer; ∑hz represents the cumulative thickness of the medium sandstone layer; Hh represents the equivalent thickness of thick mudstone; Hz represents the equivalent thickness of medium sandstone; ∑hz represents the cumulative thickness of medium sandstone; Hn represents the equivalent thickness of claystone; Hzx represents the equivalent thickness of medium-fine sandstone; and ∑hzx represents the cumulative thickness of medium-fine sandstone.

[0064] 5) Select the final equivalent lithology

[0065] The equivalent lithology of the roof and floor is determined separately. The priority of the equivalent lithology of the roof and floor is compared, and the one with the higher priority is selected as the final equivalent lithology of the target coal seam.

[0066] Preferably, S8 specifically includes:

[0067] The rock strata information in the borehole columnar section is transformed into a structured rock strata data table, which includes rock strata number, lithology name, layer position, thickness and dip angle parameters. Based on the equivalent lithology conditions, the lithology within the equivalent range of the coal seam roof and floor is identified. Finally, the equivalent lithology results of the roof and floor of each coal seam in each borehole are output, forming a unified equivalent lithology determination database to support mine gas prediction.

[0068] The present invention, which adopts the above technical solution, has the following prominent features compared with the prior art:

[0069] This method enables efficient extraction of strata information and rule-based classification of equivalent lithology. It automatically parses borehole columnar section data, extracting strata numbers, lithology names, stratigraphic positions, thicknesses, and dip angles. Combined with pre-defined equivalent lithology determination rules, it identifies the equivalent lithology of the roof and floor of each coal seam, constructing a structured data table. Driven by a rule engine, it achieves batch processing of multi-bore data and outputs equivalent lithology results, forming a unified database. By integrating borehole columnar section image recognition with strata parameter quantification models, it automates the extraction of strata information and the determination of equivalent lithology, significantly improving data processing efficiency and result consistency, and providing reliable geological basis for gas prediction at different mining stages. Attached Figure Description

[0070] Figure 1 This is a flowchart illustrating the method for determining the equivalent lithology of the top and bottom of a coal seam based on borehole columnar section information in an embodiment of the present invention.

[0071] Figure 2 This is a schematic diagram of the borehole equivalent lithology determination system in an embodiment of the present invention. Detailed Implementation

[0072] The present invention will be further illustrated below with reference to specific embodiments. The purpose of this illustration is solely to provide a better understanding of the invention. Therefore, the examples given do not limit the scope of protection of the present invention.

[0073] like Figure 1 As shown in the figure, this embodiment presents a method for determining the equivalent lithology of the top and bottom plates of a coal seam based on borehole columnar section information, including:

[0074] S1. Extract information of all straight line objects from the DXF file of the borehole column chart, identify vertical and horizontal line segments based on the geometric features of the straight line objects, and construct the table framework of the borehole column chart based on the vertical and horizontal line segments.

[0075] In practice, this includes:

[0076] Parse the straight line entities in the DXF file of the borehole column diagram to obtain the start and end coordinates of each line;

[0077] Calculate the slope of each line and combine it with a set threshold to distinguish between vertical and horizontal line segments. For example, the slope of a vertical line segment is infinite and the slope of a horizontal line segment is zero.

[0078] Based on the horizontal coordinates of the vertical line segments, determine the boundaries of each column in the table and establish a column range index. For example, if the vertical line segment to the left has X=10 and the adjacent vertical line segment to the right has X=30, then the two constitute the range of one column.

[0079] Based on the vertical coordinates of the horizontal line segments, determine the boundaries of each row in the table, and construct the table framework by combining the column range index and the boundaries of each row; for example, if the upper horizontal line segment Y=20 and the adjacent lower horizontal line segment Y=30, then the two constitute the range of a row.

[0080] S2. Extract information about all text objects from the DXF file of the borehole column chart.

[0081] In practice, this includes:

[0082] Parse the text entities in the DXF file of the borehole histogram, including single-line text (TEXT) and multi-line text (MTEXT), and obtain the text content and the coordinates of the text insertion point;

[0083] By combining font, layer, and location information, invalid annotations, such as map titles and scale bars, are filtered out, and text in the title layer is directly excluded, thus retaining text related to rock strata parameters.

[0084] By using character encoding recognition and Chinese word segmentation technology, key fields such as layer number, dip angle, true thickness, and lithology name are extracted, such as "layer number 1", "dip angle 3°", "true thickness 2m", and "coarse sandstone".

[0085] S3. Determine the horizontal coordinates of the insertion points for the four header texts in the text object: layer number, dip angle, true thickness, and lithology name.

[0086] In practice, this includes:

[0087] The text elements with table header features in the location file are usually at the top of the table. The layer number, dip angle, true thickness and lithology name keywords are matched based on the text content of the text elements.

[0088] Obtain the horizontal coordinates of the insertion points for the four header texts: layer number, dip angle, true thickness, and lithology name. For example, "layer number" X=15 and "dip angle" X=35. Establish the correspondence between the header texts and the horizontal coordinates of the insertion points. For example, the column with X=10-20 is "layer number" and the column with X=30-40 is "dip angle".

[0089] Combine column range indexes to correct column header coordinate deviations. For example, if the X coordinate of the column header is slightly off, adjust it according to column boundaries to ensure accurate division of column areas for each field.

[0090] S4. Based on the determined horizontal coordinates of the insertion point, the header text is placed into the corresponding column area in the table frame to complete the data matching of layer number, dip angle, true thickness and lithology name.

[0091] In practice, this includes:

[0092] Compare the horizontal coordinate of the insertion point of each text object with the column range index to determine the column range to which the text object belongs; compare the X coordinate of each text with the X coordinate of the header of S3 to determine which column it belongs to (for example, text X=18 belongs to the "layer number" column).

[0093] Match corresponding cells based on the vertical coordinate range of row boundaries to achieve spatial association between text content and table structure; determine which row it belongs to by the Y coordinate (e.g., text Y=25 belongs to row 2);

[0094] Correct misaligned or missing items according to the increasing pattern of the layer numbers to ensure that the data rows are completely aligned. For example, if the layer numbers should be 1, 2, 3, and 2 is missing, then add it; if there is an extra 4, then check if it is misaligned.

[0095] The final result is a structured stratum parameter table indexed by stratum number and containing fields for dip angle, true thickness, and lithology name.

[0096] S5. Traverse the data corresponding to each row of cells, extract the layer number, dip angle, true thickness and lithology name data, and construct a list of rock strata information.

[0097] In practice, this includes:

[0098] Read the matched structured data line by line, and extract the dip angle, true thickness and lithology name of each line in order of layer number;

[0099] Standardize the text content of each field, unify the units and expression formats. For example, unify the units: some write "2 meters", some write "2m", unify them to "2m"; unify the expressions: such as "coarse-grained sandstone", "gravelly sandstone", "coarse sand" unify to "coarse sandstone".

[0100] For missing or outlier values, interpolation from adjacent layers or estimation based on geological patterns is used to fill in the missing or outlier values. For example, if the dip angle of a certain layer is not written, the average dip angle of the upper and lower layers is used instead; if the true thickness of a certain layer is written as "100m", which is obviously abnormal, it is corrected according to geological patterns.

[0101] The information is finally compiled into a complete list of rock strata, which serves as the basis for identifying the roof and floor of coal seams and classifying equivalent lithology.

[0102] S6. Identify coal-bearing sections based on lithology names in the strata information list, and determine the location of the target coal seam and its adjacent upper and lower strata.

[0103] In practice, this includes:

[0104] By using language processing technology to analyze the lithology name field, coal-bearing fields and variant expressions, such as "anthracite", "coking coal" and "coal-bearing mudstone", the coal-bearing strata can be identified.

[0105] The coal seam intervals are divided according to the continuous distribution of the layer numbers. For example, if the layer numbers 5-7 are all coal-bearing lithologies, they are a coal seam segment. The location of the target coal seam is located, and the lithology names and true thickness information of the adjacent rock layers above and below the target coal seam are extracted to construct a sequence of adjacent rock layers with the target coal seam as the core.

[0106] Misjudgments are corrected based on the chronological order of sedimentary rock formation. For example, sedimentary rocks are generally "older at the bottom and newer at the top". If the rock strata below the coal seam are newer than those above, it is a misjudgment and needs to be corrected to ensure the accurate relationship between the rock strata above and below the target coal seam.

[0107] S7. Analyze the lithological characteristics of the roof and floor within the set range of the target coal seam according to the set geological rules, and determine the equivalent lithology of the roof and floor.

[0108] During implementation, according to pre-set geological rules, the lithological combination within a certain range of the coal seam's roof and floor is analyzed, ultimately determining the equivalent lithology of the roof and floor (converting multiple lithologies into one that has the greatest impact on gas outburst); specifically including:

[0109] 1) Determine lithological classification

[0110] Based on the gas storage capacity and permeability of lithology, the lithologies with different names in the borehole column are divided into 6 categories: coarse sandstone, medium sandstone, medium-fine sandstone, fine sandstone, claystone, and thick mudstone.

[0111] 2) Determine the range of the equivalent rock strata.

[0112] Taking into account two factors: first, the range of the conventional roof and floor affected by mining activities as determined by the theory of mineral pressure; and second, whether there is contact with thick layers of medium-coarse sandstone in a specific area outside the conventional roof and floor range, as detailed below:

[0113] Tunneling condition: Equivalent thickness L of bottom plate f =3+2k f Equivalent thickness L of top plate r =5+3k r ;

[0114] Longwall mining conditions: Equivalent thickness F of the bottom plate f =5+2k f Equivalent thickness F of top plate r =10H≤40+5k r ;

[0115] Where H is the target coal seam thickness; k f It is the equivalent peripheral influence coefficient of the base plate. It mainly considers whether there is contact with thick medium-coarse sandstone within 2m outside the conventional top and bottom plate range. If there is contact with coarse sandstone and the thickness of coarse sandstone is not less than 5m, the value is 1. If there is contact with medium sandstone and the thickness of medium sandstone is not less than 8m, the value is 1. Otherwise, the value is 0.

[0116] k r It is the equivalent peripheral influence coefficient of the top plate. It mainly considers whether there is contact with thick medium-coarse sandstone within 5m outside the conventional top and bottom plate range. If there is contact with coarse sandstone and the thickness of coarse sandstone is not less than 5m, the value is 1. If there is contact with medium sandstone and the thickness of medium sandstone is not less than 8m, the value is 1. Otherwise, the value is 0.

[0117] 3) Determine the ranking priority for equivalent lithology naming.

[0118] Based on the degree of influence of various lithologies on gas outbursts in the mining space, the priority order is as follows: coarse sandstone > thick mudstone > medium sandstone > claystone > medium-fine sandstone > fine sandstone;

[0119] Special cases: When the mudstone layer is the immediate roof and its thickness is 0.6-2m, it is named claystone, with priority after medium sandstone and before medium-fine sandstone; if the thickness is ≥2m, it is named thick mudstone, with priority after coarse sandstone and before medium sandstone; if the mudstone layer is not the immediate roof of the coal seam, it is not considered. If it is below the coal seam floor, it is ranked after fine sandstone.

[0120] 4) Set equivalent lithological conditions

[0121] The equivalent ranges for coal seam recovery and tunneling roof and floor are determined separately:

[0122] Equivalent conditions for coarse sandstone: Hc = ∑hc + 0.5∑hz ≥ 3m;

[0123] Equivalent conditions for thick mudstone: the mudstone layer is the immediate top, and Hh≥2m;

[0124] Equivalent conditions for medium sandstone: Hz = ∑hz + 1.6∑hc ≥ 3m, and there is no equivalent thick mudstone.

[0125] Equivalent conditions for claystone: The mudstone layer is the immediate top, and 0.6m ≤ Hn < 2m;

[0126] Equivalent conditions for medium-fine sandstone: Hzx = ∑hzx + 1.4∑hz ≥ 3m, and no equivalent claystone exists;

[0127] Equivalent conditions for fine sandstone: None of the above equivalent lithologies exist;

[0128] Where Hc represents the equivalent thickness of coarse sandstone; ∑hc represents the cumulative thickness of the coarse sandstone layer; ∑hz represents the cumulative thickness of the medium sandstone layer; Hh represents the equivalent thickness of thick mudstone; Hz represents the equivalent thickness of medium sandstone; ∑hz represents the cumulative thickness of medium sandstone; Hn represents the equivalent thickness of claystone; Hzx represents the equivalent thickness of medium-fine sandstone; and ∑hzx represents the cumulative thickness of medium-fine sandstone.

[0129] 5) Select the final equivalent lithology

[0130] The equivalent lithology of the roof and floor is determined separately, and the priority of the two equivalent lithologies is compared. The one with the higher priority is selected as the final equivalent lithology of the target coal seam. The system for determining the equivalent lithology of boreholes is as follows: Figure 2 As shown.

[0131] S8 outputs a structured rock strata data table and the equivalent lithology determination results for the roof and floor of each coal seam.

[0132] In practice, this includes:

[0133] The rock strata information in the borehole columnar section is transformed into a structured rock strata data table, which includes rock strata number, lithology name, layer position, thickness and dip angle parameters. Based on the equivalent lithology conditions, the lithology within the equivalent range of the coal seam roof and floor is identified. Finally, the equivalent lithology results of the roof and floor of each coal seam in each borehole are output, forming a unified equivalent lithology determination database to support mine gas prediction.

[0134] This invention provides a technical solution for the efficient extraction of strata information and the rule-based classification of equivalent lithology. The method automatically parses borehole columnar section data, extracting strata numbers, lithology names, stratigraphic positions, thicknesses, and dip angles. Combined with preset equivalent lithology determination rules, it determines the equivalent lithology of the roof and floor of each coal seam, constructing a structured data table. Driven by a rule engine, it achieves batch processing of multi-bore data and outputs equivalent lithology results, forming a unified database. By integrating borehole columnar section image recognition and strata parameter quantification, it achieves automated extraction of strata information and determination of equivalent lithology, significantly improving data processing efficiency and result consistency, and providing reliable geological basis for gas prediction at different mining stages.

[0135] Example

[0136] We have a DXF format column chart of an exploration borehole in a coal mine. We need to determine the equivalent lithology of the roof and floor of coal seam #3 (longwall face) in this borehole. The thickness of coal seam #3 is known to be H = 3 meters. After preliminary analysis, the strata information list (key fields) generated from the borehole column chart is as follows:

[0137]

[0138] 1. Determine the equivalent rock strata range (mining scenario)

[0139] Top slab analysis:

[0140] Equivalent thickness F of top plate r =10H=10×3=30 meters (≤40 meters, meets the requirements);

[0141] Within 5m of the conventional top and bottom plate area, there is no coarse sandstone with a thickness ≥5m or medium sandstone with a thickness ≥8m, therefore kr =0;

[0142] Final equivalent thickness F of the top plate r =30 + 5 × 0 = 30 meters.

[0143] Base plate analysis:

[0144] Standard base plate range = 5 meters;

[0145] Within 2 meters outside the conventional base plate area, it comes into contact with coarse sandstone of layer number 6 (true thickness 7.5 meters ≥ 5 meters), therefore k f =1;

[0146] Final base plate equivalent thickness F f =5 + 2 × 1 = 7 meters.

[0147] 2. Determine the equivalent lithology of the top and bottom plates

[0148] Roof equivalent lithology determination:

[0149] The equivalent range (30 meters) of the top plate includes rock strata numbered 1-3, analyzed according to lithological classification and equivalent conditions:

[0150] Layer 3 is the immediate top, with lithology of claystone and a thickness of 1.5 meters (0.6~2 meters), which meets the equivalent conditions for claystone;

[0151] There are no rock strata that meet the equivalent conditions of thick mudstone, coarse sandstone, medium sandstone, and medium-fine sandstone; therefore, the equivalent lithology of the top plate is claystone (priority 4).

[0152] Base plate equivalent lithology determination:

[0153] The equivalent range (7 meters) of the base plate includes rock strata numbered 5-6, analyzed according to lithological classification and equivalent conditions:

[0154] Layer 6 is coarse sandstone with a true thickness of 7.5 meters, ∑hc=7.5 meters, ∑hz=0 meters, and Hc=7.5+0.5×0=7.5≥3 meters, which satisfies the equivalent conditions for coarse sandstone. Therefore, the equivalent lithology of the bottom plate is coarse sandstone (priority 1).

[0155] 3. Determine the final equivalent lithology

[0156] Structured stratigraphic data table: contains all fields from the above table and supplementary information such as stratigraphic position;

[0157] Equivalent lithology determination results: No. 3 coal seam (mining) - roof equivalent lithology: claystone, floor equivalent lithology: coarse sandstone, final equivalent lithology: coarse sandstone.

[0158] The technical solution of this invention can automatically parse borehole columnar section data, extract stratum number, lithology name, stratigraphy, thickness, and dip angle parameters, and determine the equivalent lithology of the roof and floor of each coal seam by combining preset equivalent lithology determination rules, thus constructing a structured data table. Driven by a rule engine, it enables batch processing of multi-bore data and output of equivalent lithology results, forming a unified database. By integrating borehole columnar section image recognition and stratum parameter quantification, it achieves automated extraction of stratum information and determination of equivalent lithology, significantly improving data processing efficiency and result consistency, and providing reliable geological basis for gas prediction at different mining stages.

[0159] The above description is merely an embodiment of the present invention and does not limit the scope of the present invention. All equivalent changes made based on the content of the present invention specification and drawings are included within the scope of the present invention.

Claims

1. A method for determining the equivalent lithology of the roof and floor of a coal seam based on borehole columnar section information, characterized in that, The method includes: S1. Extract information of all straight line objects from the DXF file of the borehole column chart, identify vertical and horizontal line segments based on the geometric features of the straight line objects, and construct the table framework of the borehole column chart based on the vertical and horizontal line segments. S2. Extract information of all text objects from the DXF file of the borehole column chart; S3. Determine the horizontal coordinates of the insertion points for the four header texts in the text object: layer number, dip angle, true thickness, and lithology name. S4. Based on the determined horizontal coordinates of the insertion point, the header text is placed into the corresponding column area in the table frame to complete the data matching of layer number, dip angle, true thickness and lithology name; S5. Traverse the data corresponding to each row of cells, extract the layer number, dip angle, true thickness and lithology name data, and construct a list of rock strata information; S6. Identify coal-bearing sections based on lithology names in the strata information list, and determine the location of the target coal seam and its adjacent upper and lower strata. S7. Analyze the lithological characteristics of the roof and floor within the set range of the target coal seam according to the set geological rules, and determine the equivalent lithology of the roof and floor. S8 outputs a structured rock strata data table and the equivalent lithology determination results for the roof and floor of each coal seam.

2. The method for determining the equivalent lithology of the coal seam roof and floor based on borehole columnar section information according to claim 1, characterized in that, S1 specifically includes: Parse the straight line entities in the DXF file of the borehole column diagram to obtain the start and end coordinates of each line; Calculate the slope of each straight line and, in conjunction with a set threshold, distinguish between vertical and horizontal line segments; Determine the boundaries of each column in the table based on the horizontal coordinates of the vertical line segments, and establish a column range index for the table. Based on the vertical coordinates of the horizontal line segments, determine the boundaries of each row in the table, and construct the table framework by combining the column range index and the boundaries of each row.

3. The method for determining the equivalent lithology of the coal seam roof and floor based on borehole columnar section information according to claim 1, characterized in that, S2 specifically includes: Parse the text entities in the DXF file of the borehole column chart to obtain the text content and the coordinates of the text insertion point; By combining font, layer, and location information, invalid annotations are filtered out, thus preserving text related to rock strata parameters; Key fields such as layer number, dip angle, true thickness, and lithology name are extracted using character encoding recognition and Chinese word segmentation technology.

4. The method for determining the equivalent lithology of the coal seam roof and floor based on borehole columnar section information according to claim 2, characterized in that, S3 specifically includes: The text elements with header features in the location file are matched with keywords such as layer number, dip angle, true thickness, and lithology name based on the text content of the text elements; Obtain the horizontal coordinates of the insertion points for the four header texts: layer number, dip angle, true thickness, and lithology name, and establish the correspondence between the header texts and the horizontal coordinates of the insertion points. By combining column range indexes to correct column header coordinate deviations, we can ensure accurate division of column regions for each field.

5. The method for determining the equivalent lithology of the coal seam roof and floor based on borehole columnar section information according to claim 2, characterized in that, S4 specifically includes: The horizontal coordinates of the insertion point of each text object are compared with the column range index to determine the column range to which the text object belongs; Based on the vertical coordinate range of the row boundary, the corresponding cell is matched to achieve spatial association between text content and table structure; Correct misaligned or missing items according to the increasing pattern of the layer number to ensure that the data rows are completely aligned; The final result is a structured stratum parameter table indexed by stratum number and containing fields for dip angle, true thickness, and lithology name.

6. The method for determining the equivalent lithology of the coal seam roof and floor based on borehole columnar section information according to claim 5, characterized in that, S5 specifically includes: Read the matched structured data line by line, and extract the dip angle, true thickness and lithology name of each line in order of layer number; Standardize the text content of each field, and unify the units and expression format; For missing or outlier values, interpolation from adjacent layers or estimation based on geological patterns can be used to complete them; The information is finally compiled into a complete list of rock strata, which serves as the basis for identifying the roof and floor of coal seams and classifying equivalent lithology.

7. The method for determining the equivalent lithology of the coal seam roof and floor based on borehole columnar section information according to claim 1, characterized in that, S6 specifically includes: By using language processing techniques to analyze the lithological name field, coal-bearing fields and variant expressions are identified, thereby determining the coal-bearing intervals; The coal seam intervals are divided according to the continuous distribution of the layer numbers, the location of the target coal seam is located, the lithological names and true thickness information of the adjacent rock layers above and below the target coal seam are extracted, and a sequence of adjacent rock layers with the target coal seam as the core is constructed. Misjudgments are corrected based on the chronological order of sedimentary rock formation to ensure the accurate relationship between the upper and lower strata of the target coal seam.

8. The method for determining the equivalent lithology of the coal seam roof and floor based on borehole columnar section information according to claim 1, characterized in that, S7 specifically includes: 1) Determine lithological classification Based on the gas storage capacity and permeability of lithology, the lithologies with different names in the borehole column are divided into 6 categories: coarse sandstone, medium sandstone, medium-fine sandstone, fine sandstone, claystone, and thick mudstone. 2) Determine the range of the equivalent rock strata Taking into account two factors: first, the range of the conventional roof and floor affected by mining activities as determined by the theory of mineral pressure; and second, whether there is contact with thick layers of medium-coarse sandstone in a specific area outside the conventional roof and floor range, as detailed below: Tunneling condition: Equivalent thickness L of bottom plate f =3+2k f Equivalent thickness L of top plate r =5+3k r ; Longwall mining conditions: Equivalent thickness F of the bottom plate f =5+2k f Equivalent thickness F of top plate r =10H≤40+5k r ; Where H is the target coal seam thickness; k f It is the equivalent peripheral influence coefficient of the base plate. It mainly considers whether there is contact with thick medium-coarse sandstone within 2m outside the conventional top and bottom plate range. If there is contact with coarse sandstone and the thickness of coarse sandstone is not less than 5m, the value is 1. If there is contact with medium sandstone and the thickness of medium sandstone is not less than 8m, the value is 1. Otherwise, the value is 0. k r It is the equivalent peripheral influence coefficient of the top plate. It mainly considers whether there is contact with thick medium-coarse sandstone within 5m outside the conventional top and bottom plate range. If there is contact with coarse sandstone and the thickness of coarse sandstone is not less than 5m, the value is 1. If there is contact with medium sandstone and the thickness of medium sandstone is not less than 8m, the value is 1. Otherwise, the value is 0. 3) Determine the ranking priority for equivalent lithology naming. Based on the degree of influence of various lithologies on gas outbursts in the mining space, the priority order is as follows: coarse sandstone > thick mudstone > medium sandstone > claystone > medium-fine sandstone > fine sandstone; Special cases: When the mudstone layer is the immediate roof and its thickness is 0.6-2m, it is named claystone, with priority after medium sandstone and before medium-fine sandstone; if the thickness is ≥2m, it is named thick mudstone, with priority after coarse sandstone and before medium sandstone; if the mudstone layer is not the immediate roof of the coal seam, it is not considered. If it is below the coal seam floor, it is ranked after fine sandstone. 4) Set equivalent lithological conditions The equivalent ranges for coal seam recovery and tunneling roof and floor are determined separately: Equivalent conditions for coarse sandstone: Hc = ∑hc + 0.5∑hz ≥ 3m; Equivalent conditions for thick mudstone: the mudstone layer is the immediate top, and Hh≥2m; Equivalent conditions for medium sandstone: Hz = ∑hz + 1.6∑hc ≥ 3m, and there is no equivalent thick mudstone. Equivalent conditions for claystone: The mudstone layer is the immediate top, and 0.6m ≤ Hn < 2m; Equivalent conditions for medium-fine sandstone: Hzx = ∑hzx + 1.4∑hz ≥ 3m, and no equivalent claystone exists; Equivalent conditions for fine sandstone: None of the above equivalent lithologies exist; Where Hc represents the equivalent thickness of coarse sandstone; ∑hc represents the cumulative thickness of the coarse sandstone layer; ∑hz represents the cumulative thickness of the medium sandstone layer; Hh represents the equivalent thickness of thick mudstone; Hz represents the equivalent thickness of medium sandstone; ∑hz represents the cumulative thickness of medium sandstone; Hn represents the equivalent thickness of claystone; Hzx represents the equivalent thickness of medium-fine sandstone; and ∑hzx represents the cumulative thickness of medium-fine sandstone. 5) Select the final equivalent lithology The equivalent lithology of the roof and floor is determined separately. The priority of the equivalent lithology of the roof and floor is compared, and the one with the higher priority is selected as the final equivalent lithology of the target coal seam.

9. The method for determining the equivalent lithology of the coal seam roof and floor based on borehole columnar section information according to claim 8, characterized in that, S8 specifically includes: The rock strata information in the borehole columnar section is transformed into a structured rock strata data table, which includes rock strata number, lithology name, layer position, thickness and dip angle parameters. Based on the equivalent lithology conditions, the lithology within the equivalent range of the coal seam roof and floor is identified. Finally, the equivalent lithology results of the roof and floor of each coal seam in each borehole are output, forming a unified equivalent lithology determination database to support mine gas prediction.

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